Call me crazy, but I think that it would be a good idea to pay the 50M release clause for Kovačić (I don't know if Madrid have a "no selling to us" kinda clause in his contract). I think his play style is very similar to Iniesta's, and he is still very young. He uses the empty space very good, and can provide excellent passes, while at the same time his shooting ability is improving (as seen in the match vs. us in the US).
After that, Dembele would be a good option instead of Neymar. He is young, fast, capable of dribbling and providing lots of assists across the entire season. As far as I can tell, he doesn't know which is his stronger foot, so I don't think that playing on the left wing would be a problem to him.
Btw, I would also very much like Valverde to use Sergi Roberto as much as possible in midfield, give him a chance to develop properly so he can inherit Iniesta on that position.