Terry did bring that up as a kind of a poll/teaser: http://electricmotorcycleforum.com/boards/index.php?topic=6208
I think there are unknowns with getting more than two BMS' to play well together. They all have to agree to close their contactors to cooperate and cell voltages could get out of sink.
What Terry did was with the 2012 platform so it's a little different but he literally went the extra mile to bring that project together.
Come to think of it, the interconnects in the main Power Pack (or the Long Brick) don't work across BMS' (one BMS handles all cell voltages through the interconnects) and that's probably a contributing integration factor.
Without OEM support, buying a long brick (which I think Terry was aware of but couldn't discuss at the time) and trying to harness it like a Power Tank would require someone to make a professional-grade harness like the Power Tank integration.
Then there's the fact that each single brick is 42lbs which is tricky to place. One on each side of the battery compartment ("BMW Boxer" style, low and forward, probably held by the crash bars) is achievable but the "long brick" is not the form factor for that so you get 2 BMSs to add instead of one.
A "long brick" might mount where the Power Tank goes if you put a larger cowling over it and had really good bracing for it. Then you'd put chargers on the crash bars.