Why would Wonga agree to that?
I don't imagine Wonga could do anything about it in any event.
They need positive PR, rocking the boat isn't going to be top of their list.
These contracts will have stuff in them requiring all players to wear shirts with the sponsor et etc.
No doubt about it, it'll form part of the contract, but if Papiss (or anybody else) absolutely refuses to wear the shirt, then IMO, he'll be on the pitch in a sponsorless shirt.