I find that I can control who goes where in formation change by designing the second tactic from the first. If for example I want to switch from a 4-4-1-1 to a 4-1-2-3 I will load up the 4-4-1-1, slide my holding midfielder down to the DM spot, the AMC down to the MC spot and save it. When I make those changes during a game, everyone stays in their correct position.