Some small suggestions for trading, most for 1.17.

Master fisher-mans could sell any kind of Bucket of tropical fish which we couldn’t know at first, or just randomly when we put them down. The trading with boats could be moved to one in expert.

Master weapon-smiths could buy copper and sell lightning rods.

Master cartographers could sell spy glasses.

And of course, leatherworkers could sell bundles, and I wish this could happen when they were just apprentice.

Another idea is for wandering traders, they could trade as "enchanted golden apple 1" + "emaralds 64" = "enchanted golden apples 2"