It's like you're describing the separation of governance by domain. For instance, instead of having a mayor for a city, we'd have a mayor of telecommunications or technology, along with a mayor of transportation, a mayor of housing and civil engineering, and a mayor of commerce.

These problems pop up with my example:

  * You still need someone to centralize the execution; people are going to want a hierarchy and to have one person at the top.
  * Having 5 mayors means paying 5 times as many people (but they'll be able to work much more in depth in their subject area) 

If you reduce those mayors down to city council members, and have another mayor, it resembles the system in place in many layers of bureaucracy.