1) No. That would require heavy changes in the editor end the engine.
2) Yes. You can open "Menu.script" and change all the positions.
3) That wouldn't be necessary. There are plenty of easy to use 3d editors. i personally use Anim8or to model and Misfit Model 3D to convert to MD3
4) They can't. There is simply no reason, they're encrypted with a simple algorithm. There were plans on adding passwords but then I ditched it as it was unnecessary
5) Unlikely. I try to keep full compatibility with older systems