My idea is to have events that promote the use of the auction house. These events would have special costumes and items that can only be acquired from the auction house in the form of featured auctions, either buy only or bid only. I would work similar to current events, but with the auction house instead of the supply depot. Doing this would entice players to spend crowns instead of CE, and thus they would sell CE more often and lower the price of 100 CE.
What these events would actually sell, I am not sure. But OOO is good at making random events with exclusive items, so I'm sure they can come up with something.
Featured Auctions is already a thing. Except right now it's just Featured player Auctions, with the exception of the Trojan and Puppy Disguises which are always there.
Using the Featured Auctions in a similar fashion to the Supply Depot sales would be good though. If it brings some variety in our lives.