So I did the logical, sensible thing and resigned from Convergence staff tonight, since someone who needs to be sitting on his butt with his feet up really isn't in fit shape to help run a consuite, much less lead volunteers by example. Maybe my legs will get better by Convergence weekend, but only a fool would bet on that possibility; the smart money says that the best I can expect is not to get worse. I'm still going, of course, and I might even volunteer for some panels and some badging...but taking up a staff position would be taking on a job I know I'm not physically fit to do.
EDIT: It turns out that petsnakereggie hadn't been aware that my legs were so messed up, which means this came totally out of left field from his POV. He's going to talk it over with danae and the rest of the consuite heads next week and get back to me; seems pretty clear that they want whatever help I can provide. So it's really up to them, and we'll see what happens.