What if they made towers untargetable in URF?

Untargetable to players and player made minions specifically.

You could obviously freeze or stack up a minion ball still, but given the new minion power mechanics relating to the average level of the team, then the team that's ahead would gain pushing power, but not as much as a 10/0 yi or xin at 5 minutes.

Which would also give some of the champions who need a fully loaded kit or items more time to stack up their gear.

Obviously you'd probably want to add some passive gold gain to offset the current clear rate of minions, but it's basically just a timed battle arena, with indirect methods of reducing the timer.

Edit: oh yeah and the removal of the revive summoner spell. Kind made it harder for teams to stop an enemy from just rushing down your towers.