Interacting with the other manager on the touchline would add a whole new dynamic to the game and add to the realism of a matchday experience. It could be similar to the shout button, but you could celebrate a goal in front of the other manager, start an argument, leave your dugout area (resulting in punishment), or even just shake hands with the other manager at the end of a game, all would be very fun and interesting to see. Touchline bans could also be implemented if you behave particularly poorly during a match. Personally, I would love to see this in a future fm version, what does everyone think?
edit: none of these would need use of the match engine but would be cool to see