I think that would require even more work, and it may not be feasable because you'd somehow have to get access to the hardware without stepping on Windows' toes...It's probably part of why DOSbox is a full emulator instead of just a hack to get access to the hardware - it's actually easier (although by no means easy) to emulate the hardware than to try to use tricks to get around Windows' abstraction layers.
It would be cool if someone were to make something like GliDOS for VESA though - make a VESA "driver" that actually is a wrapper that routes VESA calls to DirectX calls. I guess that might not work though because many games probably try to access the hardware directly in conjunction with using VESA, and also VESA may be too low-level to be able to be translated to DirectX.