That's pretty neat, in this context (though that means seeing Capt. Britain lead a team of Avengers ain't happening anytime soon).
As far as other non-mutant characters, we know Fox has the rights to Henry Gyrich, who's generally much more involved with the Avengers. The large extent of his involvement with the X-Men -- aside from a couple storylines in the 80s -- was mostly an invention of the 90s Fox cartoon.