In my shit opinion, if we stop the main flow of emeralds into our server's economy, everyone who has villagers on their bases will grow their prices and THEN we are definetly ruining our economy with inflation and shortage of items.

Villagers at a spawn are a possibility for EVERYONE to make profit, so you're providing everyone an equal chance to get easy profit and move the economy.
By setting a trade limit older users who have already made stacks of emeralds, will easily take take over the economy by controlling most trades and the money.