Rykka 说:
I know in Warband it was difficult if not impossible to have a troop tree split off in three+ directions.
you can do that on Warband already. We dont know about Bannerlord and wont for another year or so, but it is unlikely you cant do it there as well
Warband is limited to 2 paths if you use the normal system. There is nothing preventing you from creating your own system (your own code), UI, etc. It is just super easy to use the 2-path system as it is already all done and ready for use, that is all.