To clarify my post, you wouldn’t be limited to only an area around your initial TC. If you want to build something far away from your starting point, simply build another TC first and then tower rush at will. But now you will have to think twice before spending that extra stone and also defend your new TC. If the new TC is destroyed, the towers either go dark or can be retaken by whoever builds another TC in the vicinity (they can be hijacked or retaken by you).
It would work in a similar fashion to Protoss pylons as someone mentioned above, but allowing for some freedoms and strategic mechanics.