Our local one put in a tunnel underneath the runway - https://www.youtube.com/watch?v=XKvSYrs0EsY

Though it looks like it might be lost to the public due to expansion plans for the airport :(

I’m not sure I follow the all-in-one schema issue? Won’t each endpoint have its own schema for its response? And if you’re updating things asynchronously then doesn’t versioning each endpoint effectively solve all the problems? That way you have all the resilience of the xml validation along with the flexibility of supplying older objects until each participant is updated.