TheRan, that is exactly how the Energica balances. tops off, bleeds down high cells, tops all off, bleeds down high cells, until it gets in range or an hour has passed between hitting recharge threshold, then it just shuts off. That last part is why sometimes if it's really badly unbalanced you'll have to cycle it, or in extreme cases, cycle over a day or so to walk them back into specs.
Active needs more parts, components, cost more, is heavier, which is probably why they went with passive, it's just easier overall. Me personally, i would rather shuffle power, but i believe the way that is wired, unless you want to throw a bunch of switches in there, is a constant on tech, and will slowly bleed power down over time, and can also cause grief when temp gradients start happening across the battery due to well, normal operating conditions at times, and they opted for no power leeches, especially when you have it in storage. Remember, the active acts kind of like a wheatstone bridge and each cell in the pack would need it's own little coil, resistors, transistors, capacitors etc. That stuff takes up a lot of room, especially in a pack that's already cramped and prone to heat issues.
Aaron