I asked in the GitP forums if 4ed could do low magic.

http://www.giantitp.com/forums/showthread.php?t=213948

The 4ed guys believe that it's pretty well supported simply by leaving out some classes. They also mention reassigning reasons for powers, which strikes me as pretty silly, but maybe works ok there.

However, after talking more with Zem, he's nervous about using any different system, and he also wants wizards- he simply wants them to be weaker.

It's likely that 4ed might actually map closer to what he want regardless- certainly, 4ed wizards do not outclass other classes. However, by default, the 4ed combat descriptions are reasonably flashy. So, unsure. But, mechanically, 4ed could support.

I don't think buying another whole set of books and learning a whole new set of rules is worth the effort. If I were to switch to anything, it would be an open source based on 3.5, but I honestly think I can get what I want with some modifications to 3.5. Ultimately, I think this will easier on everyone else.