I would recommend adding charge undertemperature protection as no li-ion cell should be charged if it is below 0°C. Lithium can drop out of solution and plate the inside of the cell, eventually causing a short circuit if it is done often enough. The P26A also has a charge overtemperature limit of 60°C.
The discharge temperature range does go down to -40°C but is limited at the high end to 60°C.
Cell aging speeds up rapidly at around 60°C and the internal temperature of the cells can be significantly higher than the surface temeprature. At around 75°C compounds in the cell start decomposing so you really want to keep them from getting anywhere near that internally.
If you are using thermistors for temperature sensing then their extremely slow response time and very poor thermal coupling to the cell can mean a big difference between the temp measurement and the actual cell temp.
The mounting of the thermistors is critical if the pack will be reaching high temperatures and the slow response time will need to be factored in if the cells are being used hard for short periods (where thermistors can’t keep up with the true temp changes).
But it’s all doable. 
Looking forward to your future updates!