I think he could i mean it could be really awesom.
Eh? Thor already is a cosmic hero. Thats how Lee and Kirby sold him, a mythological, a cosmic, an everything hero. Ego's first appearance in a comic? Thor. Galactus origin was told where the first time? Thor. Think of how associated Celestials are with Thor. Heh heh though I agree he should be spending more time out there exploring the Universe, I really liked Astonishing Thor mini series which was the last proper space Thor story I remember liking - not counting Matt Fractions run, but it tried.
Thor is both a mythological and cosmic Marvel character. They just have him hang out in Midgard because he is "the son of Gaea" and he has an affinity for Earth. Plus, he's an Avenger.
I find Thor more fascinating when he's traversing the cosmos and dealing with problems in other universes and encountering other cosmic characters (like Silver Surfer, Gladiator, etc.).