Infinite Community Small Maps to 1 Big Map

Fuse "Steam Community / Locally Stored" maps together, and make bigger maps.
This will make it a piece of cake to be making Towns/Regions/Countries.
Proper UI for directly previewing and integrating maps from Steam Community, for emphasis on speed of creation.
Maybe a secondary mini-UI, to even fuse only parts of a map as an option, basically the concept of Nested Prefabs but directly pulled from another map.