I haven't personally, but it's been done, with D20 Modern.

Frankly, I would have gotten far away from D&D long before now – but that pretty much sums up exactly my position on gaming at this point, "as far from D&D as I can get."

But if I'm stuck using what I can only assume is a 3.5 version inheritance, and I know the characters are going to want to go across the multi-verse and I need to be able to cover it, let's consider the options.

1. You are going to have to decide how the world works from scratch, then try to keep those rulings consistent, then watch them traipse through and ignore most of what your going to do anyway, and it's a lot of dead weight.

2. Go pick up Wushu (which is absolutely free and worth every penny of it), spend the 2 to 5 minutes that it would take to translate every single one of your characters into Wushu mechanics, let the hyper-cinematic fast action fall where it may come and then watch them nearly beg you to run your basic D&D game using the Wushu mechanics.

3. That solution is really only interesting if you really want to run a superheroes game. As reasons to run a superheroes game goes, that one is perfectly reasonable. But less interesting.

4. If you're going to get start playing D&D anyway, you might as well use the right tool for the job: D20 Modern, which has rules and guidance for all that sort of thing.

Personally, I would take that group down the Wushu path without even a blank. That is always going to give better role-play than pretty much any of the competition.