Put a manacost on Jayce's R to "force" the tearbuild
Jayce is a champion which kit is far too powerful in the earlygame if he builds straight damage. A Jayce with Ghostblade first item can simply oneshot any champion in the game with full combo, with very few champions able to respond. When Jayce builds tear, his early/midgame was closer to balanced (but still strong!), and his lategame was not so bad.
Put a cost on his transform, and make it give a Tear-stack again. That should effectively smooth out his powercurve, and remove him from the autowin lane-status he is in now.
vs full AD team, it's so broken! "Forcing" tear is okay IMO - look at Cass, playing her with no tear? Nah... But if her manacosts were halved so she didn't need tear, she would be incredibly broken, a bit like Jayce is :)