Hmm... Then, it must be mirrored 4 times over 8000h ~ FFFFh, which is 32k ROM region of NES hardware.
(6502 requires the rom to be addressable at FFFBh ~ FFFFh)
I guess we can assign a new mapper number to these 8k PRG roms, and ask emulator author to support it. These are easy to emulate, which can be as simple as mirroring an address range 4 times. There are, as you know, a lot of spare iNes mapper numbers.
The only problem is that there is nobody who's in charge of standardizing iNes mapper numbers.
I don't know but MESS team may do this?
(But don't count on me asking them, though

. I'm too shy for this. )