may be better to make ultimate solution for genesis? may be not very cheap, but super damn extremely powerful!? solution without any compromise, where features is the only target. i love genesis so much and always want to do something for genesis. it is my favorite system and was a object of my childhood dreams for a long time.
how about instant loading, 16mbyte SDRAM, ym2413 synth for sms, ramcart for cd, eeprom saves, extra mappers support for sms, firmware loading from sd, support of huge size ROMs, like 10mbyte hacks, may be even snapshot saves and emulation of systems like nes (with fpga help, of course)
NES is another good system, but i don't ready to jump in mappers hell yet (: probably i will buy powerpack for my nes , that's all