Let’s just put this on the table where we can see it. Vance Astro is so cool you have no idea.
In the original comics, he was the first person to fly into space out of our solar system, headed towards some planet that could have life on it, Alpha Centauri. And it takes a thousand years to reach it. When he finally gets out, it’s past the year 3000, and there’s a bunch of people and aliens waiting for him; technology had advanced past lightspeed levels in the time since he went in, and now he couldn’t even survive in the atmosphere without a suit, or else his body would oxidize.
Then the Badoon alien dudes attack all the planets in the solar system, take over Earth, and kill most everyone on Jupiter, Pluto, Beta Centauri, where entirely new species of genetically-altered humans lived. Now Vance Astro and his 3 companions, the crystalline dude Martinex, giant dude Charlie-27, and blue dude Yondu Udonta, who were all now orphans in the galaxy. They team up to guard the galaxy from evil…. especially the Badoon jerks. There’s also Starhawk, who is a weird time travel-type guy.
Anyway, Vance Astro eventually gets Captain America’s own shield, has cool mutant powers where he can make psychokinetic blasts and blow stuff up with his mind. The fact he’s like Space Captain America is already reason enough for him to be in the movie, as it would help normal moviegoers connect the movie as a Marvel one, and not just a spacey movie.
Plus, he was on the modern Guardians of the Galaxy team near the end of its run. It’s not like it’s a stretch to add him!
I would also be ecstatic to see the other members of the original Guardians of the Galaxy team make their way into the movie, though I doubt that’ll happen. Still… A person can dream.