The problem with MagiC64 is that AFAICR it is mostly written in 68k asm and it is very dependent on the native chipsets. Porting that to MOS or AOS4 isn't really viable.
Frodo is OK on systems that are fast enough (most classic Amigas are not), and is certainly easier to port to AOS4 (it already has a MOS port I believe, though I could be wrong).
The other alternative would be to port VICE, which is by far the best C64 emulator around at the moment, but there may be issues with that.
