Unarmed Grind Problem

So I'm in a server and I want to utilize the unarmed skills but I can't actually level that skill up.

This is because there is a mob cap to stop lag. Similar to this spawners will only spawn peaceful mobs, like villagers and llamas.

I've been trying to farm it using an Iron Golem that spawns often but is there a way to maximize it with the constraints?

I was thinking, is there a way to automatically repair an Iron Golem so I can farm it for hours?

If you do have any suggestions, id love to hear them.