i think that a mixer with the features that you are describing in 10hp simply does not exist.
Cosmotronic has some feature packed mixeres in reasonable hp
i'm really not willing to induce any gas. but i would not try to fit more voices and add a mixer in your case. you certainly don't want to remove utilities to add voices.
maybe it's time to think of expanding the hps ?
or maybe get a 1010 bluebox desktop ?