In the latest snapshot the whole trading system changed. Villagers now restock their trades twice a day, and most trades can only be done 4 times. This is a huge problem in cases where you need to trade in mass (to get emeralds, for example). 12 trades per day is not enough, even more when most selling trades only give you 1 emerald.
So my idea to fix this is to increase the frequency in which they restock their trades as you level them up.
Novice starts at 2 restocks per day and it goes al the way up to 24 restocks at Master (or something like that). I feel like this amount brings it almost back to the trading speed we've had until now. Having to afk lots of minutes waiting for the villager to restock only 4 trades would be a very unwelcome change so with this method it would be fixed.