One thing to consider is that the original design on ACS 4 apparently intended the developer to subtype a particular object type, and store all the dynamic attributes there, rather than extending an existing type.
I think it is useful to store the extended data in the same table, but there needs to be some way for the managing package to cleanup after itself and remove the additional attributes, if the package is dropped.
So I think keeping track of where the dynamic attributes came from is definitely useful.
