Yeah, it would sure help managing larger empires, as well as seeing your grouped units fight smarter. However, it would have to be working a bit different than just repositioning them.
New ships would constantly fly into the focal area. They would have to use a sort of priority target and kill it, then move on. If one would really go deep into making a smarter AI, it would be to include knowledge of the own group, as well as knowledge of what's in the planet area.
As an example, if many hangers are in the system, and the group is low on anti-fighter/bomber capabilities, they would focus on killing the hangers first. And so on...
As this would be a group AI behaviour, in my mind, it wouldn't affect the AI of the units in the group in any major way. Once the group AI decides to go kill a hanger, it send the group there and direct the fire of the units that does best damage versus the target to attack it, while letting the other units do what they do. And all along staying within the area of operations decided by the group AI.
I hope a solution is found