Defining URIObjects with a metaclass

Instead of saying

  URIMembership = URIObject(...)

I want to say

  class URIMembership(URIObjectMeta):
     url = '...'
     ...

and get the same result (i.e. URIMembership should be an instance of class
URIObject with the same attributes set).

It would be very nice if I could say 'class URIFoo(URIObject)' and get an
instance, not a subclass, so that I wouldn't have to remember two different names.

The reason for my wish is that exuberant ctags doesn't index global variables in
Python code, so I cannot use jump-to-tag or tag-completion on URIs.

Sane people might veto this request on the grounds that it is too magical.