i hope we never see achievements in ren x! i cant think of one thing i have seen in online gaming the last couple of years that has been simultaneously most pointless and detrimental to game play....and Please do not make their requirements for any special items gear or otherwise, even if they are just different models or textures. All this seems to do is drive the majority of people to forget playing the game, work only on achieving the achievements to git the new stuff. and thin just start playing again effectively making the achievements rather pointless IMO. the ONLY way i can see it being fun, even just a little bit, is if all the achievements are secret, thin it is less likely for people to immediately ruined a perfectly good game are trying to achieve them one by one but rather would over time achieve them in the natural course of the game....
i dont really have any thing wrong with achievements themselves, and they can be about fun/ funny.... but looking at BF2 to TF2, i have seen nothing but bad results and little added fun. so who knows, maybe you can develop a way that will impress me