As usual, let me start with an example.
Proposed gameplay feature: Rout
The idea is that the opponent's team does not simply disappear when the opponent summoner is defeated. They instead rout. The opponent's units are then in disarray and cannot be controlled any more (if the said opponent is a player). They flee towards the nearest exit: the border of the battlefield if open (i.e. not a wall), the next door, etc. Only if someone stands between them and that exit point will they attack him, and this only until the path gets clear (enemy defeated or moved away), or until another path as short gets clear (for instance as teh result of being knocked back, or moved by a gravity spell). If the battlefield is an enclosed space, the units will flee their opponents, always moving to the farthest space from any enemy.
Proposed Development Priority: 5
There is no reason for giving this higher priority. It would only add to the fun, keeping the game interesting in the long run as it renews itself. This could also open a few interesting new situations, based on how many opponent units do manage to flee. For instance in a single-player campaign they main regroup in the next room, making it tougher if you did not properly cleanse the previous room from opponents. Or there could be player vs player challenges based on trying to let as few units flee as possible, from the same starting point.