yes but DirectX contains proprietary code from graphics cards' manufacturers. therefore you won't be able to create a new API without doing reverse engineering.

What about OpenGL and going on from there. Even Intel said that D3D (I can't say the real words on these boards ) isn't the best in the world. They stated specifically OGL because of the arrangements they can make on vertex data to optimize code for the MMX/SSE/++
The whole D3D would have to be rewritten to achive this, but I can't remember the articles title

OpenGL is pretty nice, but doesn't offer support for developing you own software based graphics code. With DirectDraw, you can gain access to the backbuffer pointer. This is really all you need, from there you can use all your own stuff to do the drawing.

As far as reverse engineering is concerned, I wouldn't even bother. To be honest, it would be far less difficult to load the display card manufactures DLL's and write your own version of DirectX than bother with trying to improve or modify Microsofts code, not to mention you can't get sued that way.