With so much of the 30+ year legacy D&D game in the SRD, I believe it is impossible to ever make a game that would be accepted by the fans as "D&D" without it being possible to alter whatever is necessary to make the Open Game version of D&D compatible with whatever product is being currently sold as "D&D" by WotC. A game divergent enough to break that legacy with the SRD is simply not going to be tolerable to anyone vested in the D&D player network. Such a radical break would almost certainly result in a 3rd party version of the game, published under a new brand name, becoming the de-facto inheritor of the D&D player network externality, coming into direct competition with whatever faux "D&D" product is being marketed, and probably crushing it.