How moddable is M2TW at present?

[Caliban]

First, some aspects of coding are clearly broken, as CA have used conditions etc in the original code which don't work in the vanilla game, and some is totally incomplete - there is a LOT of this in some cases (about 50% of the traits & ancilliaries files), and it's simply a waste of their time putting in so much material into the game which never works for the 99% of players who don't make or use mods.

I'm not aware of any 'broken code' in M2, if you have found something that you think is a major bug, please drop the details to us at
bugs 'at' creative-assembly.com.au and we will look into it more closely.

. is it known yet wether MTW2 can support more factions then RTW?

Yes, M2TW supports upto 31 factions I believe.