He started 1 game in the WC. Against Brazil having just turned 20 years old, and did good enough, but Croatia was unlucky. Hardly justified to say he was "shit in the WC".
Verratti, Pogba and Thiago are all unavailable. OK, Pogba might be available for 125m euros...
Its either Kovacic or Lucas Lima. Do you know of any other midfielders that are available and not CL tied who are better than those two?
He didn't play only against Brazil. He also played against Cameroon (20min) and Mexico (30minutes). I don't care if he's only 20 years old. You give 10min to Verrati and he can outplay a midfield.
Pogba for 125m ? Where did you hear that ? I don't think that you know what you're talking about here. No one rated Paul at 125m euro.
Concerning Thiago, I don't think that he's unavailable. His contract ends in two years and I'm pretty sure that if we guarantee him a starter position in our team then he'll be glad to come back. His family (mother, sister, grand-mother and brother) live in Barcelona.
And to answer to your last question, Yes. If the club want Koke, they can pay his buy-out clause (58m euro). He's MUCH more better than Kovacic or this Lucas Lima lad.