I mean, think about it! Both the SMS and 84+ CE have similar CPUs, and if the 84 is powerful enough to emulate the GB, it really shouldn't be much of a problem. I honestly would LOVE to just be able to play STH and Alex Kidd on my calc, even if it's the inferior verisons.
Just like the GB, the graphics driver probably isn't the same as on the 84+CE, and it would have to support any instruction the SMS/GG have the calc don't support natively, but other than that, that's not a crazy idea.
On that, a lot of old computers (mostly CP/M based) also uses a Z80, I'd like to see CP/M ported on the 84+ as an OS.
I'm fairly sure it would run fine.
RAM would definitely be a factor if you want to make well anything on it...Pretty sure something like SMS_SDL could have ran on it (albeit slowly) if it wasn't for the low amount of RAM.And not a lot of people are called calc84maniac on earth. (nor do they have the patience for that)
Even if you somehow manage to have the CPU taken out of the equation, there's still the fact thatyou need to emulate the VDP chip and those are more complex than the good old game boy.