I thought it was a pretty nice touch to bring back some of the old CP9 moves. Didn't someone comment about a lack of that in this war so far?

Also, as far as the original CP9 cast showing up, that would be highly unlikely. I suppose the anime-only viewers wouldn't ever know about it, but in a side adventure story, the CP9 members recovered and decided to leave the organization to find a secluded home for them to live in peace.