OK, let us just assume you figure out some clever way to be able to stop registrars making an agreement with each registrant to acquire their domains at no cost if they choose not to renew. Everyone else, not being a registrar, will be able to make such an agreement it seems.
Anyway, most domain names will now be deleted. What will happen? All valuable domains will, as soon as they are deleted, be registered by the same pool of registrars. These registrars have partnered up with Snapnames, Pool, NameJet and so on. So all these domains will find their way to the same auctions but not one of these domain names will keep their age.
The .com registry:
Verisign.com
central
