I've been eying the Dark Eldar too. I am very excited to play them. Originally I was making an Eldar Pirate army using the Craftworld codex, but now that this book is coming out, I hope to make a number of ambiguous models that can be used as either Defender Guardians or Warriors and Storm Guardians or Witches. I think the key is going to be getting enough Eldar Lasguns and Las Pistols (which neither army uses but could represent shrieken or splinter weapons).

I think the Bikes will be the easiest, just magnetize the underslung weapon and add a few guardian helmets... Hope it doesnt come off as a cop out :/ But then again it isn't like I'm just adding Goat Heads to my marines and calling them whatever I want... hehe