I don't know if he really thought this through to go to war against the club. It might feel good for him to be defiant now, feeling insulted in his honor for being publicly degraded to the third goalkeeper. But does he realize the consequences of his actions?
The press in Spain is not merciful. Laporta will allow them to tear him to shreds from this point onwards, paint him as the biggest betrayer since Figo. His easy and calm life in Barcelona will be over. The same way the people lift you on the streets if they love you, will kick you down when they start to hate you. Especially because his children are in the city as well.
The club can publicly degrade him further. Take way his captaincy is only the first step. They can forbid him to train with the team, to foce him to train with Barca Atletic. If he refuses, fine him.
The players that support him, will stop doing so, once they realize he actively harms the registration of their new teammate for the only reason of being salty.
And then let's not forget how he ended the last season as captain. Didn't travel with the team to Milan as the only player, again for being salty. Refused the traditional season-end speech, which is a spit in the fan's face and rumours were, some journalists wrote kindly about him, because he/his camp feeded them with intern information.
He should really think this through, if it's worth for him to become a public enemy of the club just to feel cocky 2 weeks, until Laporta finds a way to register Garcia anyways.