Also, isn't it worth giving Sandro a shot on the left of a 3 man attack, with Lookman/Vlasic or Mirallas on the right?
Funnily enough I was thinking exactly that when I ate my lunch just now.
Going a bit off topic here, but I don't like Rooney, DCL or Sigurddson being played out wide. I also don't think Rooney has got the pace to be a number 9 anymore.
So for me - we should be playing DCL or Niasse as the centre forward.
If we are playing 3 upfront we do what you have suggested - ie play wide players in the wide positions.
Or we play one upfront with one of our natural number 10s behind - ie Rooney or Sigurddson .
Then in midfield if we are playing 3, then one of them should be Davies or Klassen as the box to box midfielder. (Or maybe both of them if we really need to go for it ? )
If we are playing 2 in centre midfield, then one of them can do the same job.... or IMO Gana and Morgan could actually work well together as a 2 if the rest of the side is more balanced, like last season.