Neither earthX nor Antigravity have external balance ports, and even if they did at least in Antigravity's case it wouldn't show cell balance for all 16 cells in one of their 16 cell batteries. What I have done is dremeled the top off of all the earthX and Antigravity batteries I have for testing and measure cell balance through individual cell voltage and cell AH capacity through both low and high rate drawdowns.
Actually opening up all these cases also gives me a chance to look at the quality of intercell connections and in the case of the earthX look at the balance circuit.
The idea of running the battery all the way down and then see how recovery goes in a motorcycle is a good idea but should be one of the last tests as it will beyond a doubt damage the battery at least some.
It is particularly applicable to modern BMW owners as the buggy basic module firmware on those bikes has a habit of hanging on without cleanly exiting and running batteries dead overnight. It only happens once in a blue moon but does happen and that blue moon may occur when ur doing a RTW.
Balance of the cells will be a big factor as if there are some cells substantially higher they will reverse the lower cells and completely destroy them instantly.
Beyond that a slow recovery is far preferable but this isn't an easy proposition out in the field though as a matter of policy if someone does this in the field with a LiFePO4 battery id recommend switching on all accessories as soon as the bike starts to make the initial charge as slow as possible.
A BMS that disconnects the battery below a certain threshold while allowing you to hit a reset button to reconnect and start would be elegant but like with even just a balancer, adds more circuitry that can fail unless very robustly designed and quality manufactured.
Ill test the batteries at the threshold where even an idiot would know his battery is running dead and then later take it all the way down at a low rate to simulate German engineers that have more fun playing with firmware then debugging it