Perhaps, but a lot of game elements for something like that are already there...after all, you wouldn't be creating new "areas" for every stadium in the game - sidelines already exist, they are just not player-accessible. Seems most of the work would just be coding a RTG game to play out slightly differently than any other game.
-Would need a sideline camera (not a big deal, Madden is doing that this year, it would just need to be lowered and behind your team's sideline)
-Physical players on the sideline and not 2D cutouts
-The ability to exit or enter the field manually after each play (it could even be a button press and whoomf you appear, controllable on the sidelines to watch the next play/s.
Maybe it is too ambitious...but it is feasible. I definitely think that by this point in this console gen, EA should have already been working on something like this to differentiate RTG. There just seems to be terrible groupthink with this mode - the lingering idea that a RTG game needs to play out presentationally just like any other game. No, it really does not. As the mode currently plays now, might as well call it "control one player". There's no sense of connection with your player - he exists only on the field when the ball is snapped, just like your entire dynasty mode team.
I think that the physical manifestation of your player - and ability to control him - on even a
limited basis off the field (whether it's sidelines, or a generic locker room area, anything) would add TREMENDOUS immersion value to the RTG mode. Just my opinion.