I would wish for a new campaign setting. Basically what I want is Middle-earth, but with a clean slate in terms of lore:
- Low-fantasy. A world where it's perfectly reasonable to not believe in giants and dragons.
- RPG Noir. Dark and gritty. Large cities are few and far between, and travel and trade are limited because it's dangerous out there.
- A long and rich history, but now the world is in decline. The accomplishments of the past are beyond the ability of today's artisans.
This setting would have its own set of classes, and its own monster manual.
So, yeah, it sounds like I'm describing C7's The One Ring but, again, I want a brand new world. (At least partly so that creativity isn't constrained by lawyers.)