Kleptolisks are an ok monster for Vaults. Frustrating if you only brought elemental, steal things from you, etc. Puts you on edge just enough to not get bland. However, while charming, there's only so much to a Vault. Diversity could spice up the cashgrab if done right.
I'm suggesting three things for this thread: Puppy variants, optional mini-miniboss fights, and rare default-type Confetti drops.
First off, Crown Puppies. My idea is to, in a way, bring back the old, invincible "Gold Puppies", with a different skin set and a different method of "attack".