Here's a crazy idea that probably won't get any support.
What if there was an item for supports that had a high cooldown like 300 seconds that made the enemy drop an item from their inventory? The icon over the item would be a faded color showing that you still own the item, but just have to revisit shop to reclaim. That way if someone is very ahead there's still a chance to get a kill and stop with the solo carrying the game.
Stats:
30 armor and magic resist
Passive: if an enemy champion has an entire tier 3 item it causes them to drop an item from their inventory that can be reclaimed by walking over and standing on the spot for 2 seconds or revisiting the shop.
buying it and removing your 