I think all Quan Chi's variations are sufficient to cover every MU tbh. Summoner dominates a lot of the cast and is probably overall his best variation, so you can rock it to most MU's. Warlock is useful for the wake-up armour and footsies against characters who deal better with the zoning in Summoner.
I think Sorcerer is great as well, but I don't know if there's any particular MU I'd use it in. It just depends if you prefer this play style over the other 2 because it's a perfectly legitimate variation.
But I do play Grandmaster Sub Zero on the side, not for MU's though, just coz...Sub Zero. NKZero.