This issue could be solved by adding a loop key to the battery box or possibly elsewhere on the board. The LED up top could likely be tied into somewhere on the V1 SBX esc/mobo although not sure about the current ability of the ESC 5V output. Also reusing those pins for something non standard could pose a danger if you put the wrong battery on the wrong board.
The magnet activation thing mentioned elsewhere is to turn the stock BMS on so that can be ignored for this job as far as I know.
If somehow we got a group of people who wanted a group buy of custom SBX battery packs I could have custom printed battery boxes for I would hope 21700 size cells.
Edit:
Oke looks like Aaron disagrees that something like
this
is possible.
