EV will not find a suited position for Griez because as you said he is stiff and plays safe. Our attack is overloaded and the 4 3 3 formation doesn't allow to properly distribute minutes between Messi, Suarez, Griez, Dembele and Fati + Perez ...
Take Messi and Suarez are untouchables Griez and Dembele will not play enough because here is Fati now as new star in terms of "give kids a chance and make a new posterboy" which he also trully deserves.
So there is 1 spot for 3-4 players.
Absolutely.
I could just add one small thing to the equation, namely that imho Dembele's ideal post is on the right. He needs a fast Semedo behind him and the entire attacking formation would be way better if Messi started from the midfield and not from the right.
That still wouldn't solve Griezmann's problems if he played as a pseudo-winger, but would bring balance.
Be frank: Messi is used to start from the right but anyway he dribbles toward the middle, which works less and less productively. It's not 2011 anymore, Messi's acceleration is still formidable but if he started more from the middle, that would be great for a right winger with considerable speed.
Even if Griezmann were the best born winger, the right side is usually empty when Messi goes to the mid, and either passes to Suarez, who falls, or to Alba. The right is not really used in attack and playing Dembele there could change that.
Of course that would invoke a 4-2-3-1 that EV would only think of 20 years after his retirement.
Valverde's "tactics" are just like his weary black jacket (fashionable in the 60's), both are outdated and Philistine...