First:
1: I’m only mashing wind so don’t get too angry, it’s bad for your heart.
2: I’m not asking for a clone of Warframe with goblins although now I that type that awesome image…
OK. To the meat.
If I was given creative control I’d import a few ideas (but far from all) things from Warframe.
What, I hear you ask all atremble, things?
Firstly instead of planets of the solar system, I’d have cities of the world that have several of their own levels. Instead of only being loosely connected missions though, each city would have its own story /s.
Then you could have a bigger choice of heroes as some heroes would be persona non grata in some areas (although you could tie that to difficulty if you had 'friendly npc’s who would also fight you).
To save years of balancing you could have the five archetypes simply reskinned for other races. Slot based so you couldn’t get 5 mages (or maybe you could in custom games?)
This would stop the ‘three of the same maps in a row’ thing that can happen now while expanding the game.
I’d also have a large open area (or 3) where you could free play as solo or group to find rare drops, crafting materials and big monsters.
Now, that wasn’t too bad, was it?