I can see Wally and Kyle crossing over. Kyle would be especially interesting, if they portrayed him as just what he was. From another earth, now stranded in the MU, but still a GL, and still doing his job. Kind of a lone gunslinger vibe, learning the players in the new cosmic setting and getting used to an earth where the heroic status quo is nothing like what he left behind.
He could def. be used to shine a light on how things work (and dont work) at Marvel.