Ideally I could do this without entering setup screen every time.
You could run speaker wire from the surround back outputs to your sub high level inputs and then on to your surrounds. Let the subwoofer handle the crossover here as your using the speaker level input. Set the surround backs to Zone 2 on the AVR. Now when you use zone 2 only the backs will play with the sub.
You'll want to keep the surround wiring for your main zone to the surrounds in place also and make sure you don't play zone 2 and your main zone at same time to avoid complications.
Basically you'll double wire up your surrounds for seperate duty......... Although less than ideal I don't see why this wouldnt work.