The very fact that they're shooting for a pg-13 rating means they have no idea what they're doing. The only way you can get that kind of rating is with graphic on-screen deaths(for instance Loki goring a dude in Avengers), profanity, or sex. None of which belong within 100 miles of this franchise.
This thing is a disaster of nuclear proportions waiting to happen. Here's hoping they cancel this thing before it gets off the ground.
The new TMNT was PG-13 and there was nothing overly violent in that movie. (Not that the movie was good mind you.)
I think the fact that it's going to be crazy action in a real world setting is why they would bump the rating up to PG-13.