It's going to be a tough sell. For it to work on an existing savegame folks would have to jump through a lot of hoops. (It felt easy to me but then I've done a lot of modding in the past.)
I'd want to involve the community in deciding on what ingredients should be required for the missing recipes too, like some arrowheads.
Anyway, I'll get a thread started on the mods forum, build a little starter mod that just fixes Josh, and post a link here. Hopefully that invokes some corollary of Murphy's Law and Larian releases crafting fixes tomorrow.