Maybe it would be possible, that at least one-filers in .prg format could run. Anyway, the most games on the C-64 are one-filers. They can be loaded completely in the memory at once and would not need drive-mechanism.
Yes, one filer is really straight-forward. You still need to use the 68000 and share the SRAM between the 6502 and the 68k.
Basically, you patch the KERNAL to skip the memory test and wait for the BASIC to start (8 VBL interrupts), then you load the game into memory by directly writing it with the 68000 (beware of endianness !).
Important : the BASIC pointers EAL, VARTAB, ARYTAB and STREND have to be updated accordingly.
Then, with a bypass mechanism that you put on the PS/2 to C64 matrix emulation, you automatically type RUN + enter.
This is pretty much how the MCC loads the first file and starts it with some little differences :
- It is a softcore NIOS and not a 68000
- The keyboard PS/2 to C64 matrix is done in SW by the NIOS (not hardcoded in HDL), this way different keymaps can be managed and the RUN + enter is easy to implement.
- The PRG file is loaded from a D64 image that resides in SDRAM and not from a file on the SD-Card.
You can also have a pretty good drive emulation by porting the SD2IEC AVR code to the 68000.
But, this is a lot of work.