I don't think that Joss' banter/humor would lend itself well to B5. And while I agree with Tulin that a redone B5 could better show the scope and scale of B5, I'd hope that the new show would *not* follow the BSG style of space battles. B5 gave us a feeling for the strategy of the battles while BSG gave us shakey-cam shoot-em-ups.
Bullshit! Galactica laid out fairly detailed plans for every major battle in the show. The strategies were clever, and played out in interesting ways. How can you not love the Battle of New Caprica?
B5's CGI was a bunch of ass, there's a reason why Star Trek still used models in 1993. It got better with time, but seriously, video games on Xbox 360 look better than some of the early B5 stuff.
There's not much point to remaking B5, it was still really good, and it told its story. The CGI in the show strikes me as one of its biggest weak points, and really, they went through and redid FX shots in Star Trek: TOS, so you'd have to think they could fix B5 if they really wanted to. The actors were uneven to say the least, but by redoing the show it would be hard not to lose something as far as G'Kar and Londo are concerned. Then again, both of the white guy leads in B5 were pretty terrible in the acting department. I think done right, a complete recast would be a net gain.
If you did go to the trouble to completely redo the show, I'd just take the basic background and outline that JMS created, and completely kick JMS off the show. Let a talented team of writers (ones that can actually write dialogue) handle it from there. I don't know if I'm qualified to say who would be the best show runner for the reboot, but I KNOW it's not JMS.