You might want to consider, if possible a full stack implementation because it might be cool… “end game” to have it so that the experience from the emulator is 1:1 what you get with a physical hardware arduboy.
It’s not important now, to get things working, but think about the ability to put the emulator on the front page and be able to present that as an authentic arduboy experience with the menu and everything.
It is obviously less important, just being able to replicate the function of having the extended memory will allow developers to make their games NOW, which is what the real need of this utility is.
After that need is met, I think it would be nice to support loading of the full flash cart if possible, and have the function of the bootloader in it. But that might be without the scope, and if it is too difficult it wouldn’t be a terrible thing, just a little sad.