At the moment there is no difference between playing FAS with a ballwinner and playing FAB but eventually there will be. If you are playing FAS and then switch to FAB the players will automatically switch positions within the fast tactic. This will ensure you always have the correct player positions on the field for each tactical system without having to use the game modifications.
All the sub categories of each tactical system accumulate experience in the main category, so if you play FAS, FAB, FAP or FAL your players all accumulate team understanding in FAS.
This "switching" will not happen if you come out of one system into another, for instance if you move from FAS to WIN you will still need to use the game mods.
You will be able to disable this "switching" if you so wish.
This will help combat situations that may occur in a game where game mod changes and sub changes don't happen at exactly the same time as you switching tactical systems.