Yeah, I imagine a target emulator is the way to go for this kind of thing.
Speaking of your last comment: while very impressive, I feel a bit disappointed when someone's done something amazing with a Game Boy or SNES or whatnot, but the solution involves shoving an entire computer in the cartridge. This is still very cool but your console just becomes a head unit for your GTX 4080 or whatnot.
That made me somewhat disappointed back in the day too, when I realized that some games had extra sound circuitry or even an extra CPU in them.