Some words of caution: If BMS fails it is often failed shorted which means that it no longer will stop overcharge or discharge. Therefore BMS is not intended to be used as a normal charge control, it should basically only cut power during emergency events. If you build a charger with PSUs then make sure that max voltage out is the correct for your battery. 12s=12*4.2=50.4V max, no higher.
On the bms/no bms question:
Unfortunately the wear and ageing of cells is an unstable process. The weakest cell get loaded harder, it ages a bit more and becomes even weaker etc so even a perfectly built pack will eventually get out of balance without BMS or cycles on a balancing charger. I have done battery builds both with and without BMS and unfortunately i have killed some batteries without BMS… It’s good practice to use them (but get a better quality one)
I agree with pacificmeisters post that a BMS cutout while far away from home can be dangerous. I ride in the winter and so far -12 deg C in the air and zero in the water is my coldest. It’s better to damage your battery than yourself in a situation like that, therefore i can bypass my bms circuit without tools if i need to. My controller low voltage cutoff is also really low, at 2.5V, after this there’s very little energy left in the battery so i would gain more distance by paddling for a few minutes extra than to set it lower and kill the battery completely.