The problem is we've already jeopardized the summer with this sporting director saga.
I don't think Griezmann hinges on Segura's dismissal, because he's Farto's transfer. The only thing that matters is Griezmann's own decision which we probably won't know for another week.
Thiago, on the other hand, directly depends on Segura getting booted. And since Farto is too lazy/stubborn to do it before the end of the month, we can only buy Thiago after the world cup. It's always problematic trying to buy star players after the WC. If Thiago has a good tournament, Bayern may not want to sell him at all or jack up the price so much that we back down. Or he could have a not spectacular WC which would take Farto's eye off him and he'll probably lose interest and move on to some other player (who likely won't be similar at all and just another name)
If Thiago gets dropped entirely because of the WC dilemma then I think our next best hope is just to throw Mina in the garbage and open up the other non EU spot for Arthur to come early. And buy another midfielder to compete.