Where is the actuation mechanism for that that though? There does not appear to be any circuitry for that here. At a minimum you'd need something that would engage/disengage the cells, either a FET or a IGBT. (the voltage drop on other devices would be too large).
For cell #1, my guess is that the 4 parallel resistors (R3) are the balancing resistors and that Q1 is a small logic level MOSFET which enables cell balancing.
On a BMS project I'm working on balancing current is only 250mA, so a small SOT-23 MOSFET is all you would need.
