Q.This is regarding a red Crape Myrtle, Lagerstroemia Indica
I just purchased a large container grown. 12 gal. Crape Myrtle. It has 10-15 nice size long stems. I hate to cut it back more than half to get the 3-7 main trunks. It is November now and I live in Tennessee. I was wondering if I could cut (saw) the root ball in half and re-root it in two containers till spring and be able to plant both trees? Would doing this kill both halves or would they both survive? My experience with crapes is that they are pretty hardy and it might work. Anyone have any luck with doing this? Thanks.

It's risky. Even if it survived the cutting through the root ball, soil borne fungal infection could set in through the open wounds and advance through the root system and root crown in the longer term.
Better not to take a chance in my opinion. Pruning of the multiple stems is a more conservative approach an safer.