Placing troops eg.) Sarleon Longbowmen, into custom groups say Fodder, the AI will not use formations and the units will not behave properly on the battlefield. Changing one unit over changes all the units over in every battle, for every lord. So every Sarleon Longbowmen you encounter in a field battle, will not function by either charinging right off the bat or standing still.
It's not a recommended thing to do.
But please ask in the Q/A thread above or if you prefer a discussion, in the General Talk thread, stickied as well.
Locked.