All in all I think it would be worth while, but I'd still like to hear from others so as not to waste (a lot!) of my time.
ReactOS would benefit as well from your approach.
From what I have read in the ReactOS forums, they don't like this approach, because they have the ability to implement real Direct3D. It's also expected to be much easier than the D3D->OGL approach, because a lot of D3D functionality is provided by the device drivers.
So, I don't think that they would benefit much.