That would definitely be a different take. A TA would be interesting. And he could even do street racing on the side or something to make him a kind of bad boy type too.
Movie related I like that idea. Brian would of course help her even though she is still pissed. Maybe in all their investigating they could even cross some of the guys the team ended up helping to take down in the movies.
One idea I had a long time ago after the first movie was of Brian going back for Mia after letting Dom go since he knew she would be all alone and he didn't want her to be. They could have even ended up leaving LA together and going to Miami or someplace else.