The current Justice League team is pretty predominantly American based. Sure, Superman is actually an alien from Krypton, and Wonder Woman an Amazon from Themyscira, but both are now based in the States, along with all the rest of the team.
If the team's goal is to protect the whole world, maybe it's worth giving the League more of a global viewpoint and outlook to work from.
And what better way to do so than by including a hero from a country with an often antagonistic relationship to the nation that the rest of the team would naturally fall back into?
Rocket Red has actually been several different people over the years (including an android, because comics!) so this could be an opportunity to use an existing version or a wholly new character that could fill other gaps in the teams not greatly diverse appearance.
Enhanced via 'forced evolution' and wearing power suits, this could be quite a different power-set for the team to play with too.