Can Jayce get a guaranteed Critical Strike instead of bonus damage on Mercury Hammer?
The bonus damage would, of course, have to be reduced to something like 30/45/60/75%, but it would open up a whole new playstyle for him and work well with Infinity Edge, Statikk Shiv, and Essence Reaver. I think you said you'd like to see more Crit Jayce when the Marksman Update came out, too. A guaranteed crit could help make that work.
Edit: I'm just suggesting that they should replace the source of his damage with another source in order to open up new playstyles and make him healthier, not rework his entire kit, people.