Okay, so there are about 100 crafting recipes. And every 8 hours, five random recipes are selected. Except... The Chess Set recipes. If you already have a Chess Piece, either in your city or in your inventory, then the recipe for that piece is excluded from the selection process. So, how about removing some of the other recipes from the rotation under appropriate circumstances. If someone has no Phoenix Eggs, why would they need Pet Food? I have no Blueprints. How about skipping the Blueprints -> Royal Restoration recipes? Now, the Royal Restoration one, I suppose an argument could be made that someone could still buy the RRs with diamonds. Oooohhh, how about a low-diamond fee for a time-window where you can be more selective on which recipes will come up?