Thanks for the detailed use-case. I've got this on our roadmap. For internal folks, this is being tracked as #1795.
I have the same request. Here's my 2 cents worth:
Just yesterday I added a custom property for Airport code. This is our method of sorting by geography. I then looked to see if I could set-up groups in Cirrus and grant permisions per property value, such as "where Airport_Code = 'JFK' ".
Then, I could set the default switch and router sort property to the same property class that the engineers are granted access (via values of that property). Then, an engineer only has to click on the property value(s) that (s)he has administrative access to -- which would show them only the routers and switches they can access -- makes it easier to find their own responsibility areas.
Here's another suggestion on the same topic: allow the Cirrus administrator to determine if the other nodes (to which access is not granted) even show up. Versus showing up but not being able to view configs, or showing up but not being able to edit configs.