The idea is a new mob similar to villagers, the caveman. They will have a smaller forehead, smaller nose and wear a tattered cloth coat reaching to their knees. They can be found in ice spikes and you have to thaw them out. You can find 5 “biome” types, cold ocean, warm ocean, below sea level, below hight level 0, and one that is its natural varrient similar to how plains villagers are. This is because of the water ruins, trail ruins, and ancient cities. They will be scared of fire similar to how piglins are scared of soul fire and creepers. They can sell you long forgotten things but with a different currency than emeralds. They will sell you items like copper tools, this will be the only way to get them. They will make pottery shards if you give them clay. They will give forgotten enchants known to modern enchantment tables, a battle hammer that can’t be crafted. And more things forgotten to time.
I’m not really sold on the ancestors of villagers being underground in random ice spikes and needing to be thawed out. If you want to do some villager ancestry thing, I feel like it’d make more sense to do that by referencing them instead of having them as mobs stuck in ice. You could have abandoned, ruined structures that resemble the villagers’ building style, with archaeological loot that strongly hints to them being villagers or at least related to them.
As for the new items, “but the lore” and “people post the idea a lot” isn’t really a good justification for adding these as trades. Let’s take copper tools for example.
Elaborating on the second one, let’s take renewable pottery shards. Yes, people would love pottery shards to be renewable, but do you think they want to have to go underground, look blindly for a rare frozen mob, thaw it out, and then come back and trade with it whenever you want to renew pottery shards? Pottery shard renewability should be reasonably accessible, so this isn’t a good way of implementing it imo.
When you’re adding new items and whatnot, you need to think about their place in the game. What do they do? What are they trying to accomplish? Is it the best way of accomplishing that? A battle hammer seems like it could a really cool melee weapon, but I have no idea what it does that separates it from other melee weapons and makes it worth seeking out.