At first I thought you meant that a group that is mirrored should automatically form a new group. Like mirror group 'Leg' and you get a new group 'Leg Mirror' or something like that.

But now i think you mean something like Components in Sketchup? Open a component, transform what's inside and all the copies of this components transform the same way?

I dont know sketchup, but thats was I was refering to for all the other commands.

But for nick, and the align tool, this is what it does now and he is looking for that tool to act as a group, not individuals.