I agree you can keep the middle beacon in overview and check it every 10 sec or so.
However I believe it is still a good idea to have a visual aid.
Any well organized sports (if we consider AT as a kind of sport) that involves such a critical penalty when you reach over a boundary, will mark that boundary clearly. It is like the field line in most of the ball sports.
We do not have such a clearly marked line and I did not ask for that because that requires engine support, and CCP probably won’t have any budget for just develop it for AT.
However now we already have a similar thing, the Abyssal boundary. It worked pretty well.
Yes, boundary violation is always a thing in AT, and it has been entertaining through out the past years. to be honest I enjoyed looking at other people boundary violate XD but as a game designer myself I do not think this is a good cognitive load for player. The more challenging way of letting player play with the boundary is not to ask them to keep in mind there is a boundary, but to allow them see it clearly, and utilize it against their opponents.
If CCP says no, then fine we won’t have it. I do not see a reason why we should not add this visual aid.