I would actually go with the 4-4-2/4-3-3 hybrid from last season. Playing Malcom/Dembele as RM/RW, who are very advanced when we attack. Messi as a RST when we defend. Our shape would change to 4-2-3-1 or 4-3-3 when we attack, depending on what Leo does. If he drops in front of the box, we go with 4-2-3-1, if he goes to the centre Suarez acts as LST and Messi as false 9.
And before somebody says that it wouldn't work, we would at least have someone to give us some width on the right side of the pitch. Currently we only have Roberto, who is often getting caught in the final third.
Imo:
Messi is worth like 2 creative players.
All other players are worth as 1 creative players.
Some are worth as 0 creative players since they aren't too useful around the box and in the box (Arthur and Rakitic, for example).
When we had Iniesta, we had Iniesta+Alba on a left=2 creative/attacking players around the box
And Messi+Dembele on the right=3 attacking players there (2+1)
Now, without Iniesta, we have no one on the left.
Arthur plays there and he is way more defensive minded and less creative than Iniesta.
So, in this season, we have:
Alba on a left=1 player
And Dembele/Malcom+Messi in your formation=3 players (Messi is worth as 2 players)
So, in your formation, our left side would rely only on Alba.
Arthur is too defensive minded and the closest player to Alba is Suarez who struggles with first touch and simple passes.
So, when "stupid" EV plays Alba+Dembele/Malcom/Coutinho on a left and Messi in the middle, center and on the right, we actually have:
2 players on a left (Dembele and Alba)
And 2 players on a right (Messi who is worth for two), helped by Roberto.
So, in some way, this tactic is actually the most balanced tactic when you are comparing left and right side.
Also, if you add Roberto on the right into the mix, who is offering more build up around the box and in the box than Arthur on the left, then we would have this in your formation:
On the left: Alba
On the right: Messi+Dembele+Roberto
1 vs 4 players (again, if Messi is worth as 2 players).
Now, if you'll ask: why have we bought Malcom then who is more suited to the right side?
Well, that is a whole different question.
I have no idea.
The answer is probably: low risk, high potential reward.
If he'll make it=awesome.
If not=an investment was worth a shot.