Why not cutting the signals from IC001 pins 31 (R), 33 (G) and 35 (B), and injecting your RGB signal directly from there?
For SYNC you just need to use a composite video input. So instead a RGB signal from IC001, you inject your own RGB there.
You can add a switcher to see the OSD from TV when necessary too. Thoughts?
Marked as 3, 4 and 5 on PDF:
