Villager Trade Rebalancing Suggestion

While it would be an absolute pain to transport villagers all across the world so they can breed and get you the correct villager type for your needs, the real problem is that even Master level librarians would only be able to trade level III books, thus removing one of the main advantages of trading with villagers.

I propose a different solution. First, if villager trades must have anything to do with the biome, only make certain trades more likely in those biomes, rather than exclusive. Next, make it so villagers can change biome type. If they stay in a biome long enough, their texture will change to match that biome, so if you bring a blank slate villager to, say, a swamp, it will eventually become a swamp villager, you can lock in that first or second level Mending trade, then move him off to another biome for his next level of trades. Second, change the way rerolling trades works. Now, simply breaking the job site block would not change the villager's trades, instead if a villager has any trades that have not been accepted by a player after five minutes, the villager can offer a different trade after it has restocked. This would work for a villager of any level. Furthermore, for librarians specifically, each level of librarian would only offer trades for the corresponding level of enchanted book. Novices would offer level I trades, and so on to Masters with level V trades. These things combined would make for a much more balanced system then either of the alternatives.