Writing stuff that runs flawlessy on all emulators and fails on the real deal is no problem. It happens every day. Or well, if NES ROMs were written that often it would... but let's just say that the majority of so-called "NES homebrews" are still emulator-only.

Good to hear you intend to make your software actaully work though. If you need to do any testing on a PAL NES, I'll be happy to test your stuff on the real deal. I don't have any working MMC5 devcart yet though, since bigger ROMs than my 16-byte test prog doesn't work with my EPROM emulator for some weird reason. But this will hopefully change...