I'd like an in-game map which fields can show up in via a flag, similar to how it works with dynmap. The in-game map does not need to be precise and I only intend to use it for a large "claim" field (allows other fields to be used only if inside this "claim" field)

This would be too much work to implement with my limited free time. Maybe you can find a dev to build it and make a pull request.