This is an interesting idea, but I don't think it does a great job of addressing the issues with the villagers.
Imo, here are the big problems with the biome-specific librarian trades:
It's really unintuitive. Enchanted books don't seem like something that'd vary between biomes, and the only other biome-specific trade in the game is a fisherman boat trade. There's nothing to hint that the trades are biome-specific, so you're never going to find this out unless you go to the wiki. Of course, there's a ton of stuff in MC like that (e.g., brewing), but I'd like to see less of that instead of more.
Many enchantments (including Mending) are locked behind swamp & jungle villagers, which don't have naturally generating villages. This makes these trades even more of an easter egg and getting them extremely annoying.
Artificial biomes don't really solve either of these problems. It's still extremely unintuitive. And even if you know how to do it, you'll need to somehow obtain a jungle biome splash potion, throw it somewhere where you have a baby villager trapped, wait for it to grow up, and then trade it to master just to get an Unbreaking II trade.
I think that if swamp and jungle villages became a thing and if there were, idk, special enchanted book textures for each librarian type, the system would work really well. It'd encourage exploration and setting up paths (e.g., Nether highways) to villages in other biomes. As for Mending, I honestly think that the enchantment's existence should really be revisited.