Very excited about the PB.
Please make a voice expander. Preferably, to keep costs down, either an internal voice expansion that can be user installed (if there's room), or an external box without the control surfaces that is Polychained... users can always do our own mixdowns of two separate stereo pairs if needed.
Alternatively, a full desktop/rack unit with the control surface, but just with good PolyChain/Sync capabilities.
Or if you see no practical way to offer expansion like the above options, just make another 12-voice version that's a little bigger... And people who buy the PB6 but want to upgrade can sell their unit and purchase a 12 in the future.
The three-voice limit for stacks is very constrained, and six voices for atmospheric/cinematic pads will have voice stealing on release.