Warren Zaïre-Emery is a super talent who I think could be immediately useful, but signing young fullbacks feels a bit pointless based on our recent past, no matter how talented they may be. I'd like to see us give Kabore or Yan Couto a shot.
It takes a lot to get into City's team at 18, 19, 20, etc. and unless you're a top 3-5 player in the world in that age range (like Zaire-Emery), more than likely they're not going to make a difference or be signed as an investment piece more than an actual player.