CASA can give flexibility to all sorts of approvals. I worked in one organisation where the CP's medical was invalid for many months - CASA simply approved him to continue as CP until the medical was restored.
Just because he couldn't be PIC, it didn't stop him doing plenty of ground check & training, and backseating to monitor the training standards on flights.
Of course, popping off the twig would present a whole new set of challenges - Don't think you'd get a temp approval to continue if they had to post it to your wooden box !!