Fullscreen "overlay" using proxy d3d9.dll?

Has any one already tried the technique of a proxy dll as described here:
Intercept Calls to DirectX with a Proxy DLL

Would it be something worth looking into?

VAC detected for modifying games, you CAN however use directdraw to overlay onto the game(which doesn't show on screenshots either).
The problem is that DirectDraw is decrapitated and is replaced by Direct2D(on win7/vista I believe).

And it uses some fancy color format called YUV on nvidia cards, making colors look all gay and shit if you use RGB(for ATI)

I'm willing to work on a directdraw version if thats what you guys want.

I was afraid it was detectable, already looking into the ddraw overlays, been using those in earlier Delphi projects...