Oh no, most of the races can be kept in the transition. Avian Elves are definitely allowed. I may have to get rid of some of the more crazy mutations, i.e. the skinless Karinthians or ice-eating Akkalik, but those can be easily transferred into other interesting things (such as the Karinthians retaining their heightened senses and the Akkalik being more-or-less unaffected by the cold).
Actually, let me make a complete list (of you 5 players

) of how I think your current races may translate into the new NES (I want it to be less bat- crazy, still fantasy, but less apocalyptic):
Akkalik- Tundra/Cold-climate dwarves who are very, very, very resistant to the cold
Bladvenn- Blood-drinking Elves, not frog-people at all (though not vampires either)
Dohtel- Not sure here, actually :~I Having them be super-men is a bit game-breaking
Karinthians- Humans with heightened senses
Malachim- Avian elves
Sheol- Forest dwelling gnomes, very apt at hiding (though no innate camouflage)