I see a thread(1) about ContactMech being related to another ContactMech, from back in October. I don't however see any implementation of using ContactMechLink(or a new ContactMechAssoc).
My suggestion would be to not create a new entity, as then we would not be following the data model books. However, I do suggest having a ContactMechLinkType entity, and adding such a field to ContactMechLink. Is there any actual implementation for this? 1: http://www.google.com/url?sa=t&source=web&ct=res&cd=1&ved=0CAYQFjAA&url=http%3A%2F%2Fwww.pubbs.net%2F200910%2Fofbiz%2F18563-question-about-best-way-to-group-together-contact-mechs.html&rct=j&q=ofbiz+ContactMechLink&ei=W3PPS8SFLoKclgeO9qSfCw&usg=AFQjCNGjnbI457QAesgx_mgdikSh6nqDWw