Werner?
I've never seen him play on the wing, but I don't see why he wouldn't be able to, as he's got the pace, dribbling and 1v1 ability to do it.
If you look at videos of his best bits, he often picks the ball up in positions we'd see Sterling or Sané in and a lot of his assists are from the same areas, cutbacks on the byline inside the box.
For example -
Also i've just seen he played 46 games of his 103 at Stuttgart on the wing, so I'd say he can play there.
The problem with Werner as I see it is that he'd cost 60, 70m+ and you can't really spend that much, break your transfer record etc. on someone without starting them most games, but then you'd cause a lot of friction with Aguero or Jesus or Sané. Maybe in a years time when Aguero leaves (Is that 2019 still or is it later now?)