Sitting in my cave full of thoughts learning Asembly
Its a bit harder than you might think.
First of you would need to hook a vtable called DrawIndexedPrimitive and SetSteamSource. Tbe easiest way (not working anymore) would be to use a detour which takes the original function and then jumps to your function then jumps back to the original one. Then you would need to get the strides and numverticies and remove the z-buffer on them and then fill the texture with a color of your liking.
Its a bit harder than you think becouse there is no avaliable hook for DIP and SSS that works.