Well I'll be honest I hated the new origin so I can pass on any flashbacks to do with that. I just hope they don't flood us with too many new characters because we all know how that will end up. I honestly feel they could go with Shredder and the foot clan a second time round introducing Casey and the utroms(maybe in disguise with a reveal at the end). Shredder and the Foot were barely explained. Shredder could open the 2nd movie with "Technology has failed me, it is time to return to the ways of our past" and then go on to create his army of ninja. I would find an army of ninja far more threating and exciting that a bunch of gun toting nobodies. When that fails bring in science in the third movie with Bebop and Rocksteady and open the door to an Utrom space saga!!!
Come On! get me in with those writers
I would kill to hear and see the turtles in a rooftop fight with ninja's from the original comic.
You know where (I think Donnie says) "these guys are good!"
and then each one it turn says "but...... we.... are..... BETTER!" and then they just kick some butt!