It's clearly not about programming, it's about gameplay. I can't see all the potential problems arising, but the most obvious is the ability to capture treasure fleets. If you're able to capture and use treasure fleets gathered on your continent, this could be exploited. If not - there will be a mess with 2 types of treasure fleets. Another one I see is the problem is how you interact with those resources. As I understand, now distant land resources exist only for civilizations from the old world, if you create symmetry here, there should be some ways to interact with old world treasure fleet resources for old world civs.