Anyone already famous as any main cast member = a terrible idea.
We have done this kind of thread before, and it always degenerates into a list of actors who are hot right now. In the real world, these kinds of movies are almost always a handful of relatively unknown stars, and maybe one or two name stars in supporting roles.
All that said: Zach Braff? He looks nothing like Marten. According to Jeph, Marten looks like a paler version of his friend Bryan. This is Bryan:
That don't look very Zach Braffish to me.
On the other hand though, if we were looking at making a movie about the people here on the forums we'd definitely be contacting Mr Braff to play a certain mod *cough*Mnem*cough*. (don't look at his more recent hairy pics, the resemblance is more striking when he's clean-shaven).