Not entirely sure if this is the right place to start this, but I figured I plan on posting fluff once I have answers to my questions and it'd be easier to just carry on an existing topic and keep it all in one place.
Righto! I love to
tear into help critique a fresh IA. ;P I'll endeavor to be straightforward, but respectful, in conveying my thoughts.
This is my attempt to recreate a Chapter I made in 4th Edition using the Traits system. The traits I took gave bolt pistol/ccw and 2 special weapons per Tactical squad, but removed heavy weapons from Tacticals as well as limiting Terminator Armour and most vehicles. Originally they were going to be a severely depleted Chapter (hence the lack of high level gear), but I have since decided that there are more fluff opportunities if I set the battle that crippled them a few decades/centuries before the current timeline, allowing me to put in some more of the ideas I've had.
"Travel light and swift, fight flexible, hit hard. Remember the Decimation! Avenge the First!" 
Chapter Name: Knights of Kydonia
Geneseed: White Scars
Training: Wolves of Fenris
I'll reserve any judgement until I get through the whole thing and get to read your history for them, but I would point out two things that might be worth some thought:
- White Scars and their successor chapters tend to be 'savage' / 'primitive indiginous peoples' / 'barbarian natives' themed in terms of culture and appearance. I can see how a concept of Knights, traditionally a heavy cavalry unit, can easily map to Space Marine bikes, but even apart from the fact that there's an unfortunately large number of "Knights of X/ The X Knights" chapters, it does mean you'll need to do a fair chunk of explaining as to how the massive swing in character and culture their name implies came to be.
- Everybody loves space wolves! It's not hard to see why. They've got a lot to love and they have great character, fluff, and crunch. But the thing is, so many people love space wolves, they seem to be spending half of their time training successor chapters from other geneseed lines these days. There's also the consideration that, while Space Wolves could account for significant culture shifts from the White Scars origin, the Space Wolf cultural influence doesn't exactly lead to anything evocative of a knightly order...
- I'd suggest dodging the old and common rut of "my chapter uses inspirations from/the codex of X chapter, so I have to work in X chapter as having a direct hand in my chapter's history." Have them be all White Scars or White Scar Successor stock, training cadre too, and just come to evolve their own differences and culture over time. If Kydonia has knightly chevalier orders, then that could be the source of it; as I mentioned, there seems to be a trend in the fluff and DIY's I've read to have white scars successors closely integrate the culture of their homeworld.
Codexes used: 1st Company - Codex: Space Marines. All other Companies - Codex: Space Wolves
Changes to Allies matrix: Eldar become Desperate Allies. Dark Eldar become Allies of Convenience. (I don't use allies, except maybe if I was having a big game and needed the points, so this if of little, if any, practical use, just done for the sake of the fluff really)
There's any number of excellent reasons for a hatred of the arrogant Craftworld scum, but I will be very intrigued to see what motivates a chapter to regard Commorite raiders as pragmatic allies, especially considering the White Scars' legendary hatred and vendetta against the DE.
Reason for Second Company onwards being Space Wolves: 2 special weapons per squad, bolt pistol and combat weapon provided, Space Vikings are awesome, the Wolves and the White Scars are similar in some respects (ie: considered reckless, especially in their Primarchs, seen as "barabaric" etc)
Not pushing an agenda, but letting you know your options- Though it seems a weird fit at first, as I suggested to another friend of mine working on a chapter with SW/White Scars theme influences, Codex: Chaos Space Marines can also do a surprisingly good job repesenting this sort of army. You can get squads of CSM with both bolter and BP/ccw, and I'm pretty sure you can get two special weapons under the right circumstances. Chaos also has fairly good bikers, of course, and the potential to load out a really face-smashy Biker Lord as a Kydonian company captain.

Reason for Eldar being Desperate Allies: Quite simple really, shortly after their founding the Knights of Kydonia came across the Eldar forces led by Farseer Kialandí and Autarch Menelyavor. .... The Knights of Kydonia took over 70% casualties, but they survived and vowed vengeance on the cowards who had hung them out to dry.
Chapter tries to be the good guys, demonstrate goodwill to the Eldar, and set aside their differences to fight the good fight... and get shafted for it. Superbly 40k! Bonus points if it wasn't just a tactical withdrawal on the Eldar's part- it'd not only be so perfectly Eldar, but be a spectacular source for the Knights' white-hot hatred, if the entire 'alliance' was in fact simply a ruse, and the Farseer had intended to lead them on, earn their trust, and then leave them and then let them be decimated from the very beginning, in order to further some inscrutable goal or another. Perhaps they had a vision that the Knights would be their downfall/cause the deaths of many Eldar, and the whole affair was their way of trying to avoid this fate by luring the Knights in to the very jaws of annihilation. Of course, it would seem this Farseer did not account for the possibility that a remnant of the Knights might survive, rebuild, and swear terrifying oaths of vengeance against that craftworld/the Eldar race...
Reason for Dark Eldar being Allies of Convenience: Long story short (I will cover the story in full at a later date), the Autarch, Menelyavor, disagreed with the Farseer's decision to retreat, feeling they owed more to the Knights of Kydonia after fighting so many battles side by side. He did not, as many Eldar on his Craftworld do, believe that that Eldar lives are worth far more than any others, even those of their allies. His continued questioning of the Farseer eventually resulted in things becoming increasingly difficult for him and he chose to take the Path of the Exodite, taking those who shared his views with him, as well as many who simply wished to take the Path of the Exodite for themselves. Eventually, circumstances drove Menelyavor to Commoragh, where he earned the respect of several Hellion clans as well as a few others, and developed a love of fighting on Skyboards...
Speaking from experience? Whenever you need to use the phrase 'long story short' to explain something about your Chapter, it's typically a Warning Sign.
I do like the idea of portraying an Eldar who, for once, decides to employ Eldar arrogance and obstinacy in the pursuit of upholding their race's ancient ideals of nobility and honor. I would, however, point out two things/make the following suggestions:
- Exodites are the 'eldar hillbillies' who live on planets, have an isolationist/'commune with nature' ideology, and tend to use lower tech than craftworlders or dark eldar. Eldar who reject the Craftworlder Paths go on the Path of the Outcaste, and while this can sometimes lead to them falling utterly and joining the DE, the other 'typical' options are either Ranger... or Eldar Corsair. A superbly well suited middle ground between the Paths and the outright depravity of the DE. Corsairs are their own masters, and fight by their own rules. Corsair fleets are also usually lead by 'Corsair Princes,' many of whom are marginal or distant descendants of the ancient, pre-Fall eldar nobility.
- Dark Eldar are depraved. Like... Seriously depraved. If Menelyavor truly joined the ranks of Commorragh, he would no longer be any sort of person Marines would associate with. Your whole schtick is that Lyavor is an Eldar of fierce honor, and honor has no place in the Dark City. However, it seems clear to me what what you're really after is Skyboards, and there's good news; Eldar Corsairs span the range from dudes like Yriel to dudes like Sliscus, and their ranks tend to include both ex-Craftworlders fed up with the Paths for some reason, and dark eldar who want a way out of the constant waking nightmare that is life in Commorragh and Kabalite life.
- I would suggest retconning Menelayvor to an honor-obsessed Autarch who breaks with his Craftworld, remains to fight by the Knights' side during the Decimation, and then leaves and becomes a Corsair Prince afterwards. This still gives him ample opportunity to come into contact with skyboard-using eldar warriors and decide hey, those skyboard things are really cool. You'd still use the DE rules on tabletop, but in terms of fluff it lets you keep Lyavor a much more heroic and honorable character, one whom the Knights could be moved to return the respect of. Because he IS a corsair, one who might well raid Imperial worlds every now and then, the Knights would never truly welcome him in full trust and friendship, but they can still work out a sort of unspoken gentleman's accord due to recognizing each other's honor and worth. I can see the Knights pulling a Commodore Norrington to Corsair Lyavor's Jack Sparrow, but Hellion Boss Lyavor I can only see them hunting down like a dog.
1) How likely/unlikely is it for an Aspect Warrior, such as a Scorpion or Banshee, to be accepted as an Arena fighter and begin to adapt to some of the Wych practices, such as not wearing any significant armour? (ie: not become a Wych, but be close enough for rule purposes?) If so, how long should such a transformation take, roughly?
Considering that Dark Eldar loathe craftworlders and delight in any opportunity to torment or belittle them, not likely. Considering that the founder of the Incubi is implied to be the fallen Phoenix Lord of the Striking Scorpions, not impossible. However, I would really suggest going the Corsair route I mention above.
2) I don't know anything about Eldar/Dark Eldar ships, but need at least a couple of classifications for the fluff I plan to write. Can anyone provide information or links for me?
Eldar and DE ships are more fragile than Imperial ships in terms of physical durability, and they don't have conventional shields. However, they are very fast and maneuverable because they use solar sails instead of conventional engines, and they are SNEAKY as all get out, using loads of advanced tech to completely scramble enemy targetting systems and appear as near-totally invisible, so that even though they're fragile they're absurdly difficult to hit solidly.
As to specific marks, Games Workshop still has the rules for the old Specialist Games like BFG, if you do a bit of digging. They're all available as free PDF files, and several contain information about specific classes of Eldar and Dark Eldar ships. The Lexicanum is also generally a good source for information, as they have fairly good articles on BFG ships.
3) Is it acceptable to use existing 40k characters into your fluff? Not planning on killing anyone off or anything, just thought it might be cool to have Blackmane or someone as part of the reinforcements that stop my Chapter getting obliterated.
It is not
impossible. However, this is generally a dicy idea. It relies very, very heavily on the skill with which it is executed, and the difficulty of doing even remotely a decent job of it goes up exponentially with how powerful and famous the character in question is. Other fans are automatically on their guard when original characters and ultra-prominent canon characters get thrown together, and even the tiniest flaw or discrepancy will often cause them to react negatively to the interaction, rather than it coming across as the super cool meeting you wanted it to be.
Ragnar in particular is one of THE most famous Space Wolves, who are one of THE most famous chapters, and his life has been held pretty thoroughly under the microscope by GW and Black Library. I would advise any interactions being fairly distant and incidental, and in general, tread very, very carefully if you venture into these waters.
Hope you found this helpful!