The trading hall has a librarian for each of the highest level enchantment books and at least one villager of every other profession. Each villager can be lowered individually to be converted into a zombie villager by the two zombies that can walk around behind the rows of villagers.
In the entrance area is an automated brewing station (design by impulseSV) and a supply of golden apples for the villager curing to lower the prices.
The beacon in the middle of the trading hall is only active during the working hours of the villagers. So it works as a work hour indicator.