My personal issue with this is that it takes the agency away from the player.
Basically a big part of this champions power budget would revolve around buffing an immobile, AI that is easily manipulated by the enemy but not the user.
Most of the time you want to be the one doing something, not buffing the tower so that it can be more powerful when an enemy stupidly stumbles beneath it's gaze without minions.
It comes down to this ability putting the power into the hands of everyone but the player. How effective the ability is really up to the tower's AI and if the enemy makes the mistake of taking the aggro of a buffed tower. The player can't force the enemy underneath their buffed tower.
However I do think anti-siege or tower based power has potential in League. Something like the beam you can control from the tower in Nexus Siege could work much better as it lets the player make the decisions and use the ability.