This type of thing might work better in the form of a ground-up project. D&D combat has so much baggage with it, what with the core rules, and all of the supplemental material. It's hard to come up with anything that won't have unforeseen consequences in some odd part of the game.
Back in 2E, something like this could have worked better, because there were no AoOs and you could get all of your attacks for a round when you moved. So, you would have had people caromming about the battlefield, but no one would be marginalized for it.