A 4-in-1 that's not Action Replay
Certainly not impossible, but I can't say I think it'd be worth the trouble. It's also possible to mod it so that A-bus dummy reads return the RAM cart ID without any RAM actually being there, but that would probably result in at least some graphical corruption (the program would probably still run because developers were forbidden from storing code in expansion RAM, and all the important data is most likely in H work RAM for the same reason).
Physically impossible.
Certainly not impossible, but I can't say I think it'd be worth the trouble. It's also possible to mod it so that A-bus dummy reads return the RAM cart ID without any RAM actually being there, but that would probably result in at least some graphical corruption (the program would probably still run because developers were forbidden from storing code in expansion RAM, and all the important data is most likely in H work RAM for the same reason).