Just an update for anyone who might be interested in physical cartridge built:
Bought and downloaded gmod2 crt, used cartconv and converted to bin , written this into 512k eprom and used regular Ocean compatible cartridge PCB. Works like a charm.
I expected maybe the game will crash once it comes to hi-score saving, but surprisingly it doesn't. At least so far, I beat 7 monsters and made it to hall of fame with no problems. Of course hi-scores will not survive the reboot and that was the sacrifice I was ready for.
Again thanks for this great party game.