Frontends already do that, in a sense. There are a few extremely good console emulator frontends. Besides, all the console emulator authors don't like their personal work grouped under a single emulator, and by large, the codebase in these said emulators and so different that it would require ridiculous amount of work to make all that code fit together. MAME has an uniform driver system; every game and system implemented uses the same layout, and every line of code has been written in the same programming language.