Given the problems with our two 80m RWs I've been thinking about this over the last week and I would definitely give it a go against a club like Palace, but the inverted winger is all the rage these days. The problem though for United is that we don't have fullbacks that can take full advantage of inverted wingers, which is partly why our attacks fizzle out once we hit the final third. When Antony and Sancho were on their game, however limited they were, they were too one-dimensional and easily defended, and without a fullback with the pace or ability to overlap effectively our attacks ended with Antony and/or Sancho had the ball. You could for the most part say the same about Rashford, who just puts his heads down and tried to burst through the brick wall of defenders, predictably without success. What makes Garnacho distinct from those three wingers is that he can beat a defender to either side.
I like the job Pellistri has done so far but ETH sees in him a shot footballer then starting Garnacho on the right would be a strong move. That said, I don't recall a single match where Garnacho was effective for a full 90.