I am not bothered by it so much. If I find a surveyor or a colony ship in my ZOC I immediately try to buy it or trade for it.
The going rate for a surveyor is about 1000 bc, and a colony ship is about 6-700. If you can afford it the surveyor will repay you many times over in the course of the game. I think the colony ship is a bargain by giving you the ship and more importantly 2.5 billion in population and one less SI planet.
Neverminding that, I can see your point and it would be fine with me if they set the limits you want. However, I doubt they will, since the borders policy has been constant throughout the game series. As for what the AI gains from all their violation of your ZOC, I could be wrong but I doubt they get much in the way of tactical advantage.