Here's a though - how about a game mode/unlock/token/whatever (stacks with VT obviously) that alows for all distinct throphy bossess to show up as random 2nd bosses instead of just ones from the core pool?
I think the random monster slot is currently tied to the 2nd boss (or the boss is tied to the random monster spawn) and I know you can sometimes get "doubles" when a dungeon has a core monster type as a default feature (I often get double gorgons and sometimes snakes).
What I'd absolutely love is to, after the main throphy questline is done, have the ability to add variety to my runs (VT ones especially) by having Vampires, Nagas, AA's, Illusions, Djinns and all the other stuff show up as random monsters. I know many of them work best and have interactions in their respective dungeons, and that some don't have bosses, but I'm kinda tired of the core pool after having played against it everywhere.
I get the whole storyline thing with throphies having their places and all that, but I'd make the game way more enjoyable and varied.
Wouldn't mind seeing Troll Bossess, a proper corrsive Rusalka boss etc. Ratlings and AA's and Djinns and all the weird stuff you have to think around, and definitely more debuffs around the map.