A simple Ohmwrecker buff to make it viable;
Let it be used on allied turrets to Fortify them.
We used to have a summoner spell called "Fortify" which was removed because it was too powerful when used in organized teams but complete garbage in solo queue. Given how weak turrets are right now, having an item that allows a player to "Fortify"(I.e. make it either highly resistant to damage or outright invulnerable for a bit while firing faster) would be extremely valuable. It would make Ohmwrecker , not overpowered, but good.