I would like UserA to be an Administrator in dnn/SomeCountry/SomeDepartment/SomeArea

But only be a Author in dnn/SomeOtherCountry/SomeOtherDepartment/SomeOtherArea

I would like the hierarchy to be easy for an end user to create and preferably light weight.
I would then like the page at the end of the tree to show a custom module based on the role.

Is this possible do this with an existing nestable content item? (folder or group or sub-site etc)

It looks like i could do this with sub-site but I think a sub-site is far to heavy for what i am looking for (lots of duplicated css etc), some type of 'folder' would be a better fit.

Is there a content type that already supports this?
Is there a module that already supports this?

If not then how easy would this be to implement?

Thanks for your help in advance

I used child portals but it isn't, as you sayd, a very good solution.

Now I'm trying to create a module to manage hierarchy. if I get good results I'll share on codeplex.