A currency exchange. If you have too many of one type of coin, you can trade them in for a certain amount of another coin. There would be set rates, of course, and you couldn't trade in any coins for red coins. I think that would be pretty cool.
I think if the message about lag pops up and cuts you off in the arcade, you should get a refund of your arcade tokens. My computer is pretty crappy and lags about half of the time, so that's half of my arcade tokens down the drain with nothing to show for it.
LOVE the idea of the energy shop. Now my only question is whether or not the energy reloads over time. Also, collecting all of the coins in the harder levels should be able to increase your max energy by a little (Leave that up to you to decide)
Lastly, I know that it's been posted a lot, but PLEASE add a world rating system.
 "Hood Episode 2"){kind=icon}
 "Coinbox Hero"){kind=icon}
 "Accelerator"){kind=icon}
 "Experimental Gameplay in 10 seconds"){kind=icon}
 "You Only Live Once"){kind=icon}
 "Anti-Idle: The Game"){kind=icon}
 "Upgrade Complete 2"){kind=icon}
 "DuckLife3: Evolution"){kind=icon}
 "Elephant Quest"){kind=icon}
 "Everybody Edits"){kind=icon}
 "Don't Shoot The Puppy!"){kind=icon}
 "Reactance"){kind=icon}
I've got the 'newest' list in my bookmarks and I try to keep up to date :)