It should be, but it would probably involve the same amount of pain in the ass that converting something from TS2 to TS3 does. I was never any good at all with hair meshing in TS2 (the alpha crap used to throw me all the time), and it's only moderately less involved in TS3. I'm thinking it may not work very well, seeing how the hair meshes in TS3 are all one group, rather than individual alpha groups, but it certainly wouldn't hurt to try converting!

Clothes would be a different story, at least as far as meshes go, since the bone names/numbers are completely different between the two games. You could convert them, but it would be a serious pain in the ass since I'm pretty sure there's no automated way of changing the bones.

(And, as always, people are more than welcome to convert any of our TS3 stuff back over to TS2!)