If I make an MMC2 or MMC4 test ROM, does anybody have a suitable PNROM or similar devcart to run it?
No, but I could put one together. I have an extra Punch-Out cart which looks like it was pulled from a dumpster so it would be perfect for this.
I don't have any MMC4 carts, I've been meaning to get 1 or 2 so I can get a copynes plugin out for it.
Only Famicom Wars, Fire Emblem and Fire Emblem Gaiden had ever used MMC4. All 3 are rather rare, and that would be a BIG shame to destroy any of them.