I think could be a cool idea insert in Solomon's Boneyard main menu a shop where you can buy, with real money or money of the game, a package that drop rare rings or epic rings, with a determined probability.
After the drop of the package you can decide if you want accept or not the rings.
If you have the scavenger's perk unlocked the rings accepted will finish automatically there, otherwise ,if you haven't it, you can use the rings accepted only in the first game you join.
I would also a daily package reward (but bad respect the previous), in order to join daily every people to Solomon's Boneyard.
This is only one idea, tell me what you think about it! ;)