Somewhat off-topic, but can you describe your usage of the Master Contact record? In almost 6 years of working with FP, I've not once had to use it and I think you're the first one on communities to mention using it.
We provide managed services to external clients, so we use the Master Contact to arrange our contacts into a hierarchy of Customer (Master Contact records) and Contacts (Contact records).
It works well for us, with the only limitation being that a Contact can only exist in one Customer (we use Email Address as the primary key for our Contacts) and we sometimes deal with shared 3rd Party contacts for multiple customers. If that 3rd Party contact uses email to create a ticket, it can be associated with the incorrect customer (Master Contact).