Journeying Journeymen

Biome-specific trades are actually a good idea, for all villagers, not just Librarians, but the community really doesn't like when farmable things become unfarmable. However, if a valuable resource like mending books just becomes harder to farm, the reaction is usually more positive.

The Journeyman stage of a villager should live up to its name by way of a new special one-time trade: the Journey. You pay the villager some emeralds (and/or other goods, like food, a map, etc.), and they go off and despawn some distance away. Some time later, the villager respawns and comes back to where it started, having reached the Expert stage, with new trades that aren't specific to the biome they're in/from. The Master trades should also be biome-independent if the villager went journeying. This would unlock Mending in any biome, but players would have to go through a lot of villagers (or be extremely lucky) to get a Mending one, instead of just re-rolling one over and over.

If you wanna minimize disappointment, the enchantments selection could take into account which ones are already offered by nearby villagers and avoid those.

Cartographers could be a special case. It really doesn't make sense for them to offer maps if they haven't been surveying, so the apprentice stage should offer no maps (put the banners there), instead all 3 stages from Journeyman on should offer a Journey trade, and after they're back from their journey they offer a new map to a random rare structure or biome.