I didn't saw the whole thread, but I disagree with Wiz objection. Sure, if the first to complete his station only has a CB and is angry that the other continued constructing his stuff, then this "Stand your ground" idea is much too powerful and removes all possibility to feel secure in our borders, but if there is something like a crisis, or if a war is automatically declared for the control of the zone if the second player persists, it seems to me most players would think before doing such a drastic thing.
Stellaris, like EUIV, is not a game where we are permanently at war, nor should we able to. War has to be carefully planned, and declaring one without sufficient preparation can be disastrous.
Besides, I can only imagine, if such a "stand your ground" feature were in the game, how close a race it would be to control systems, and how entire fleets could be mobilized in order to dissuade the other player to stand his ground. It seems to me this would be a plus on gameplay, if it were done on the model of crisis, neutral zone areas or chain of events which could lead to an unplanned war declaration.