I'm a bit confused, why do you say this would require AI changes? Pursuit battles already involve the deployment of frigates from the flanks, all we're doing here is expanding the number of ships that can be a part of that flanking manoeuvre.
I meant not the battle itself, but the actual sector map. Defeated fleets generally still follow your fleet to 'maintain contact'. So I do not mean the battle, but the sector, the place where you can interact with planets, stations etc.
E.g. when you defeat a Detachment, usually a few frigates/destroyers survive the battle. If you let them go, this small fleet remnant will follow your fleet to maintain contact, blocking you from opportunistic raids on planets. (I am talking about the stage of the game, where you are strong enough to defeat detachments, but not yet strong enough to defeat fleets together with a fortress)
Right now, instead of letting go, you can ask any ships to auto-combat them via the second-in-command option. However, if only burn level 9+ ships could be used for this auto-battle, it would effectively cripple the players ability to make quick raids.