I like this idea. Here are a few commerce options. the format is:
Commerce Group Offering the Deal
XXBP - the amount offered to the kingdom to enter into the deal followed by a brief description.
Game Mechanics: The kingmaker kindom modifiers or consequences.
Farmers and Merchants of Rostland
15BP - Annual rights to cultivate a farmland for export, tax free
Game Mechanics: Kingdom does not reduce consumption by 2 BP for the negotiated hex
Merchants Guild of the One Eyed Witch
10BP (Used only for Black Market) - A special tax free zone (including import and export duties) and a hands-off policy by the local spymaster for a period of one year.
Game Mechanics: Instead of the +2 Economy benefit of a Black Market, the kingdom incurs a -3 Economy penalty for one year.
Lumber Consortium
70BP/year - A ten year contract with the Lumber Consortium for exclusive logging rights to a woodland hex which lies within one hex of a water source capable of accommodating a large transport ship. The Lumber consortium will have the option of renewing the contract at the end of the year. The woodland hex must be cleared of all inhabitants and the kingdom must continue to secure the hex. The Consortium will build a mill on the water. The Consortium will also build a pier on the water. The kingdom may not build another mill in the kingdom but will have the option to purchase the mill if the contract is not renewed. The kingdom agrees to purchase all lumber from the Consortium while under contract, however the Consortium guarnatees only locally harvested lumber will be sold to the kingdom. Building an additional pier is subject to the approval of the Consortium and the use of the pier by the kingdom will be subject to usage fees. The Consotium will build and maintain a road through the woodland hex and the hex in which the water source is located. The 135 initial lumberjacks will not be subject to military service for the kingdom and will work with representatives of the Consortium in the case of violations of law in the kingdom's cities prior to incarcerating any Consortium employee. The Consortium will appoint a separate Marshall with jurisdiction for the hex under contract.
Game Mechanics: The kingdom may not build a mill and incurs a -2 Economy penalty monthly to pay the Consortium for local lumber processing. The kingdom does not incur the base value for the Pier and costs to the Consortium for the use of the Pier incur a -2 Economy penalty monthly. If the kingdom builds a city in a hex adjacent to the wooded hex under contract, the kingdom incurs a -1 Unrest penalty monthly for the first year due to the unique nature of the Consortium relationship with the kingdom, especially the presence of a separate Consortium law.