Isn’t part of the reason they’re thinking about recasting Jefferson, besides the spin off, because Jefferson is required for some important scenes in later episodes this season and Sebastian Stan wasn’t available?
The impression I got from the article was that Sebastian wouldn’t be able to commit to the spinoff, so they wanted to recast Jefferson for an appearance at the end of this season, so that then that actor will have been introduced on Once, before they throw him into being the lead of the spinoff. I didn’t get the impression that Sebastian wouldn’t be available to shoot an ep for the end of season 2, it’s just that they’re planning long term, and if they wanna get a Hatter pilot done by next season, they’ve gotta change the Hatter’s face before the end of this season.