Game code would need to be rewritten to account for the display frame rate. AMH uses 15 fps. RZ+ is 30 fps.
When I first started on RZ I did use the same pinheck board as AMH for color, so it's technically possible.
The other issue is the amount of code used to get RZ color working. RZ color doesn't leave much room for extra code on AV side. AMH uses the AV code heavily for certain aspects of he game. Something I ended up decoupling for RZ. This is kinda of why AMH has AV and Firmware versions that are the same, and RZ code versions are way different.