Ok, you convinced me, but it's not one of these basic clones we had lately, this one adds a new mapping for the rom, it's not mapped as the others, so I'll need to look into it in more detail...
Congratulations for the motivation though !
Ok, it was not so complex finally, the neogeo system is full of hacks, the mapping of the code rom is :
from 0 to 0xfffff normal basic mapping for 0x100000 bytes
then if the size is > 0x100000 you get something more
0x200000 to 0x2fffff rom bank and then if there is a write in the 16 last bytes of this region (which is rom so the writes are supposed to be ignored), then it's supposed to be a bankswitch based on the byte written to be able to access any address > 0x200000
This one uses the mapping at 0x200000 but not the bankswitch and its size is > 0x200000
it adds a new area which was unused so far :
0x900000 - 0x9fffff code rom starting at 0x200000 !
I tested it, it seems to work, assuming the code doesn't try to access any address beyond the end of its rom it should be ok, it seems good for the small test I did. I'll post a binary later, you won it. You should take a look at the git log for adding this rom, it's not so hard to do, except here I added the mapping for 0x900000 plus a new define rom ROM_END instead of copying lines all the time... So that you'll be able to add your own clones later !