A proposal for incentivized self-capping: https://steemit.com/steemit/@alexgr/thoughts-about-capping-rewards-in-an-incentivized-way
You choose what your max reward will be. The lower you go with your max reward setting, the bigger the multiplier of your earnings is.
Possible problems: Complex to explain.
I haven't thought of any game-theory issues that might lead to gaming.