I have located the video output on the non-campible games with VGA, and I think maybe they could be easily fixed, but my little experience allows me to move forward ...
I have tried with the game Deadly Sky Pal Multi5, and I have found this
0.000 (1st_read renamed)
offset 0x170ABC
It seems that this function is the one that takes care of the video out, and best of all is that it is found in all games, although in some they change their values
These are the changes that I have done and this is the result
0x170BE4 Change to B0 FB 9A 8C
0X170BEC Change to B4 FB 9A 8C
Result
The emulator game appears as VGA 480P 60Hz, but only half screen is displayed on the left.
In console the screen appears in black and only sound is heard
This could be the beginning so that all games can be fixed, although clear is that you still have to change some more values
