Bajahammer,
My last pre did what you were wanting and I liked it. I could set everything to small and get your typical results, but if I want to listen to 2-channel full range I could switch to bypass and it was great. No signal to the sub.
I vote for this functionality when they do the firmware update, but who knows what will be released.
I write software for a living and we always have to nail down full requirements, and then code a product. It would be cool if such requirements were spec'd out and released, then their developers could make the appropriate firmware changes. But, it is kind of just a wait and see thing I guess.