Barca dont need old school wingers who basically dribble with head down and pump cross after cross into the box which is why he wouldnt be a back up to Neymar or Messi in my opinion. Regardless of the formation Barca are not going to play the wide players in that way.
The Balotelli comparison is only about him never developing as a player despite countless managers thinking they can change them
Not even advocating Vidal as back up but he is more a team player than Deulofeu and will work much much harder defensively.
He will not be a backup to Messi or Neymar obviously, but when barca wants to stretch the field a little and give some extra width a true winger will be of great help. Keep messi in the midfield and have neymar and a winger on left and right wings. It is no surprise that MSN flourishes in middle, no crosses and no bullshit. But an alternative wouldn't hurt, but i am not sure if that would even work against a complete packed defense. Deulofeu would be useless then, he doesn't have the capability to force mistakes from defenders. Deulofeu is not the winger we should sign, he is below average but a true winger definitely can help barca.
I did not suggest that we should sell Vidal or something, he is definitely more valuable to the team Deulofeu will be. But i would like Roberto to play in midfield and Vidal to compete for RB with the new signing.
If we sign both Deluofeu and Bellerin it would kill me though, that right wing is just suicidal and is such a downgrade from messi and alves. It is either Deulofeu or Bellerin, can't handle both at the same time.