Since zombie villagers can no longer be cured, they are basically regular zombies that cannot spawn with tools or armor and have no chance of dropping anything other than z-meat.
Given their low spawn rate, I think it would be an interesting change to their loot table if they could drop items they might have used in their former professions as normal villagers. A piece of coal, or paper or leather etc. representing one of the 5 villager professions: blacksmith, librarian, butcher, farmer, priest.
It would make them a kind of rare spawning loot mob that people would want to hunt down on sight, instead of just avoiding or running away from.
This is assuming of course they do not already play some kind of role in the upcoming HC Villager addition.