This is a popular concept, every newb (or his dieing brother if you are like some) will ask about this at some point in time. Analagy (I never claimed I could spell :-D ):
You have a pen that writes thin, a pen that writes thick, a marker, and a piece of chalk. They all have things in common, some more than others, but you'd never try to combine them all together. Its not possible to do it and achieve good results. They all 'write' different.
The plugin system came the closest to possibly combining the emus, removed a LOT of the differences between emu's. Video, sound, and controller imput now ARE all combined.