I would also be using Lipos until they are nearly exhausted
Not unless you like replacing them often you won't. That is what the alarm is for, to discourage or better yet prevent discharging beyond the point where damage will happen. If it was a type that ceased supply at the low battery point, that would be the "no more bullets" (thank you Elmer Fudd) point.
The manufacturers generally produce high capacity batteries by connecting banks in parallel. If they are all at the same voltage at the time of connection, they just act like one big battery without any undue drama at the time of connection. Afterwards, they continue to act as one unit. If you are using a laptop, the proof of concept is in front of you.
I still think that NiMH are better behaved and rather less fragile, even if their capacity is lower per unit of weight.
Never thought of using thermistors as heating elements - I only ever came across them when used to suddenly change from high to low resistance when they were presented with a high voltage where the sudden drop in resistance on heating, and the subsequent increase on cooling, was of great benefit.