I propose that players should have to have unlocked a Tier 0 skill before being able to learn a Tier 1 skill. Same for tiers 2, 3 and 4. Maybe this could be a "feature flag" in the server configuration?

This game is plagued by people that refuse to do any collection of their own. Many often wait for higher paying skills to unlock, and profit on the backs of those same individuals that unlocked it for them. I would like to see the game incentivize everyone to contribute to the collection of raw materials.

This could also be solved by a more standard "skill tree" approach: Where to take carpentry, you have to already be a logger. Skill trees have the added benefit of making the game more "new player friendly".