Since S3 was just starting filming, they could probably do first block at least. The scripts for the seasons are done, but its on-set adaptations and fixes that that can't be done. If it was late in filming in reshoots, that would be very difficult without writers, and if it was earlier in the process and the season wasn't written yet, it would be very difficult too. But right at this point, they can probably do a fair bit of the filming and hope that the strike is over by the time for reshoots comes for block 1. There will probably be more need than reshoots than usual, so that means keeping sets intact. Hopefully there's not a huge number of sets to build and take down.