Externalities imply economic inefficiency. That some goods will be supplied in greater quantities than optimal or less quantities than optimal. You can't derive

Externalities imply economic inefficiency. That some goods will be supplied in greater quantities than optimal or less quantities than optimal. You can't derive much more from externalities. Most externality models aren't complex functions that try to start from some conclusion and try to create an inverse function of the conclusion to support the conclusion. They are often just a simple linear cost model. For example carbon taxes are just a constant price with a transition period to allow adjustments over time. It doesn't get simpler than that. Even the more complicated land value tax often just is a constant percentage of the land value (85%). The question is what the land value is but even then it is often just using some average prices based on recent transactions with small, less than 100% adjustment factors depending on local factors. The model complexity again is constrained and does not allow infinite complexity. The conclusions you can draw from a land value tax don't go beyond the money the government spends on maintaining and building new infrastructure.