This is not enough, new balanced cells without BMS may be can be used for months/years with luck without any error. But they should not be used in such way.
LiFepo4 cells are very "rugged?" but they can differ in SOC depending from many variables. Beginning with temperatur differences from the one side of the Pack to the other, than the differences in aging or SOC and capacitiy differences at the beginning of usage of the accupack.
The fact that the voltage alone is not very meaningful to determine the "real state of charge" SOC makes it even harder to balance this cells. But there are hard limits which should not heappen to the cells. Undercharge and Overcharge. If you have 15 full charged cells and the 16th one has only 2,5V and you discharge the block, the Inverter thinks "all is ok, the Pack voltage is high enough" but in reality this 2,5V cell will be discharged under 2,5V and can be also inverted in voltage. It can get an negativ voltage and instantly die. For this case it will be good to have the BMS to switch off before something like this will happen. Also the BMS can warn you if the temperatur for charging this cells is to low or to high. Or it warns you if one cell loose charge because of an internal Cell error. All this resons are enough for me to use an BMS.