Porting DRM and hardware accelerated graphics drivers can be done without any changes in userland Haiku code at all. Just add accelerant that setup framebuffer for app_server and make OpenGL render to offscreen GPU buffer, copy it to BBitmap and draw with BView::DrawBitmap. DRM drivers can be located in HaikuPorts and be optional. Any architecture improvements can be done later.
I already suggested that in Hardware graphics acceleration port idea.
Interacting with DRM to enumerate screens and setup framebuffer is not difficult. Porting Wayland feels more difficult for me and there are no need in it at all.