Re: Which members of the Guardians of the Galaxy should join the Avengers?
None of the ones announced for the GOTG movie need to be Avengers, ever.
Of the comic-book GOTG that apparently don't get the call for the big screen: Mantis, Moondragon, and Vance Astro are the only ones who have done stints with the Avengers. Other than those three, there's no crossover with the Avengers at all.
THE COTTON AVENGERS
...They move like slick cotton on oil.