Great to hear about the postal-address package. So the last big chunk of work is creating template widgets. Since these require a number data model packages as dependencies, we may want to make this a separate package that extends the acs-templating package functionality, rather than commit to acs-templating directly.
As far as addresses types, there is a postal_types table for keeping track of things like mailing vs street address, etc. So app packages could use a mapping table for one (party_id) to many (street, mailing, etc) address relationship mapping. However, I'm wondering if a more general solution is to use acs_rels. Mark Aufflick is working on a UI for acs_rels right now.