It works! Hardware took some time to get going, but software was a snap.
Currently just using the default timings for WVGA display (800x480).
Need to adjust these, but it works!
Just populated and baked this expansion board today. It's got a BT816 EVE3 GPU coupled with a ADV7125 3-channel DAC.
There's also a couple tiny chips to select sync signals between P2 and EVE. It's rigged so can output VGA either from EVE3 or P2.
Screenshot isn't the fanciest, but I don't have any way to push the button