I think the current proficiencies cover most every topic known to our pilgrims, except for one: Finance and Economy. As such, I am suggesting a new proficiency related to the matters of trade and profit:
Markets and Mercantilism (Working title)
Minor Bonus: Deep Pockets
For each point in M&M a pilgrim has, he can carry 1 percent more in his purse.
Example Inspirations:
Piece of 8: Occasionally received when selling to NPCs instead of a silver piece.
Gold Doubloon: Craftable from 8 Pieces of 8, or found while digging in sand once glass industry is implemented
El Dorado: High-end Fish
Lucky Penny: Occasionally spawns on paved ground like an herb.
Example Craftables
Bear Marquette: Bear Steak + Herbs (I just love the name)
Bull Marquette: Cow Steak + Herbs (when cows implemented)
Purses
Small/Medium/Large Trading Stands
Barter stands
Silver Sinker: Fishing tool crafted with silvers and iron, good at catching El Dorado.
Example Skills:
Aristotelian Economics: Unlocks other skills
Bulk Purchasing: Unlocks purchasing discounted stacks of goods at an NPC (1800 for 10 glass panes, for example)
Barter Economy: Allows barter stands
The Chartered Company: Allows selling advanced resources to the old world?