What about a cast that includes hybrids? But not in our traditional sense (Eric/Danielle, Mark/Mallory), but hybrids in the shows that they've been on.
Like Rob/Amber are hybrid Survivor/Amazing Race, Jeff/Jordan, Brendan/Rachel, Cody/Jessica are hybrid Big Brother/Amazing Race
I could see TPTB doing something along the lines of:
2 pure BB
2 pure Surv.
2 pure TAR
5 assorted multi-show teams
It would help 'keep balance' while still having 11 teams (also opening the door for Romber/Brenchal/Jordeff/Jody/Keithney to return)