The fact that spawners can now be owned by all ranks and can be bought in donor shops is, I believe, detrimental to the economy. Here is why.

Mob eggs - before anyone could get spawners, people prided themselves on farms. People would have horse or mooshroom farms that were very profitable (partly because of the head market). As a result, eggs were worth a fair amount. I can't really remember how you got eggs, I know one way was in the dungeon. Maybe you could also get them from voting, I'm not certain.

Drops - with spawners being purchasable in the donor shops, virtually all drop markets are harmed. Sure, this makes drops cheaper for new players, but it also makes it harder for them to earn money.

Heads - the market for mob heads used to be very profitable. I once saw a slime head sell for 160k at auction. Last week I bought one for 12k. Removing non-vanilla Spawners would help in restoring this market.

Spawners - The spawner market is currently controlled by those with large balances and large shops, with little room for new players to make money. However, were this implemented, spawners found in dungeons in the wild would be worth much more money, which would be better for new players.

Another step that might be necessary would be for the server to buy the existing non-vanilla mob spawners from the players that have them. This would be difficult indeed, and put a lot of money into the economy, but I believe worth in the long run.

I thus propose that removing spawners from the donor shop and perhaps buying all the existing non-vanilla spawners from those who have them would be very beneficial to the economy. The changes, of course, wouldn't be overnight. There are still tons of mob heads that were once very valuable floating around, and it would take time, as it always does, for the drop market to get back on it's feet. But, given time, I believe the market would recover at least some of it's former value.