In regards to Tordesillas, it is worth noting that historically, Protestant maritime powers like England and the Netherlands, and other third parties such as Catholic France, did not recognize the division of the world between only two Roman Catholic nations brokered by the pope. Really, the treaty was mainly used by Spain and Portugal to avoid conflict over their overseas expansion, and even then it was enforced only if the other kingdom's interests were at stake. Spain did not care about Portugal's colonization of Brazil across their side of the meridian, but did start to argue about the treaty when Portugal discovered the Moluccas, which were one of the richest sources of spices. Portugal did not oppose the Spanish expeditions to the Philippines due to their lack of spices, but raised issue to the Pope when other Catholic nations tried to stop Portugal's expansion to the east by claiming the meridian (and therefore Spain's share of the world) ran around the world.
The treaty was historically important in dividing Latin America and shaping how the colonial empires of Spain and Portugal took form. However, it became obsolete when the other European nations started to colonize North America (and later Asia and Africa), and since the Spanish and Portuguese nations' power were in decline at that point, they were unable to hold and enforce their claims to much of the world, making the treaty as good as nothing.
As such, the Treaty of Tordesillas mechanic should probably be reworked completely.
- Instead of making it an universal Catholic mechanic, Tordesillas should be a mechanic exclusive to the first colonizers limited to the first half of the game, which usually will be Castile/Spain and Portugal.
- Once the Colonialism institution spawns or the "Discovery of the New World!" event has happened, the event "Treaty of Tordesillas" takes place, dividing the colonial regions among the first two explorers/colonizers of the new world. Generally, all Colonial regions apart from Colonial Brazil and the Philippine Charter will be assigned to the stronger colonizer (usually Spain), while the other colonizer will get Colonial Brazil and the rest of the Trade Company Regions (usually Portugal).
- Colonization of the colonial regions will grant +10 global settlet increase, as usual. Colonization of the Trade Company regions would now receive the same benefit.
- Rather than immediately triggeting the penalty "Violated the Treaty of Tordesillas", if a Catholic/Protestant/Reformed/Anglican nation colonizes an area which another nation has a colonial claim to, the nation which the area has been assigned to gets an event which allows them to either let the other nation continue their colonization process, or press their claims.
- Should the claimant of the area choose to ignore the colonization long enough that another colonial nation is formed in the area, they lose the claim to the entire colonial area.
- Should the claimant of the area press the claim to the colony, the colonizer gets three options: granting the colony to the original owner, selling the colony to the original owner, or ignoring their claims. Only the third decision will lead to a violation of the Treaty of Tordesillas and will always grant the claimant of the area a claim to the province, but the severity of the punishment from the treaty varies depending on the factors described below.
- Catholic, Protestant, Reformed and Anglican nations can choose whether to respect or ignore the treaty. The AI should almost consistently choose to ignore the treaty (as nations historically did), and apart from the initial colonizers, their subjects and the Papacy, only Catholic nations of lower government rank that are too weak to oppose the initial colonizers' hegemony should choose to respect the treaty.
- The negative modifier "Violated the Treaty of Tordesillas" only appears immediately for a nation which already has colonial claims in another region: meaning that if Spain and Portugal are the two colonizers, the negative modifiers only occur if Portugal expands to Spanish-claimed lands and refuses to yield the colonies, or vice verca.
- If a Catholic colonizer has chosen not to respect the treaty, they get a significantly smaller opinion penalty from the Papal States and no settler growth penalty. The claimant country's opinion penalty remains unchanged.
- If a nation with its capital in a colonial/trade company region converts to Catholicism, it receives no "Violated the Treaty of Tordesillas" penalties. Colonizers retain their claims to the region, however, but are significantly less likely to press them.
- After the Age of Absolutism begins or if enough nations have started colonizing without the initial members of the Treaty of Tordesillas attempting to stop their colonial attempts, the Treaty of Tordesillas becomes invalid, and all European nations can colonize without any penalties. The initial colonizers lose claims to the colonial regions where they haven't established a colonial nation, as well as their claims to all Trade Company regions.
- As long as the Treaty of Tordesillas is valid, Catholic/Protestant/Reformed/Anglican AI nations are significantly less likely to take Expansion or Exploration ideas or pursue colonization; if an AI nation respects the treaty, they will not take Expansion or Exploration idea groups at all. Equitably, once the Treaty of Tordesillas ceases to be valid, the AI will be more likely to pursue colonization.
All of these changes should hopefully make the Treaty of Tordesillas mechanic more historically accurate by ensuring that the colonial game flows relatively historically by having different colonizers starting to pursue colonization at roughly historically accurate time-periods, while also giving players enough tools to overcome the restrictions brought by the Treaty of Tordesillas and pursue earlier colonization, if they so choose to.
