Back in the days MA mentioned "tradeable mining claim-deeds" will be introduced. Lets say u got a "2k ped hof in pvp4" and are afraid to extract it. Just sell it to Uber No.1. :p In 2005 (VU 7.6 update) MA said "You cannot trade mining Claim deeds at the moment. This will be fixed shortly." It never happened. Also I miss a bit of diversity on deed design. ;p
Sounds like one for content of oblivion to me. Better stick the CLD land system in there too while you are at it ;)