Most likely regions will have their own coordinate systems, with a transformer
of some kind linking them.
There is some good work being done by a guy called Jonathan Burns, at Latrobe
University in Melbourne, with completely generic coordinate systems.
The nice thing, the really nice thing, is that different rules could apply in
different regions, you could look down on a plane and see many copies of
yourself echoed across it like a hall of mirrors, and all sorts of things.
This is very much an Escher framework.
Jon Holdsworth