3. David Montgomery/Antonio Gibson
It does not really matter which of the two running backs, if the Chiefs were to trade for a back that is as talented as either David Montgomery or Antonio Gibson then they would become a much more dynamic offense. Heck, you could probably even throw Kareem Hunt in the mix as a potential back the Chiefs could add.
Clyde Edwards-Helaire has not been as good as the Chiefs would have hoped in recent weeks and adding a consistent ball carrier would add a new wrinkle to this offense. When the going gets tough, teams are going to be able to play the two-high shell against Kansas City as there is no threat of running the ball.
If you add someone like Gibson or Montgomery that obviously changes. Both guys certainly could be traded before the deadline with the situations they are in. Khalil Herbert has been pounding on the door to be the Bears' RB1 while the Commanders seem more interested in Brian Robinson as the main back.
Some may put a receiver like Chase Claypool on this list but that shouldn't be feared. Not only is it unlikely, but it doesn't really change much. It would be just another slightly above-average (but not great) receiver for Patrick Mahomes to throw to.
Getting a surefire running back would be more impactful for the Chiefs and would make them harder for the Chargers to stop.