Spodman, the scenario you give an example of is the situation at the present time. Why can’t each aircraft quote a GPS distance from a location (as they can do with DME) and then let ATC use a more enlightened form of separation, rather than 10 minutes?
Dick, Spodman is talking about getting vertical separation achieved before they pass, which is 10 minutes before the estimated time of passing. No GPS/DME kit will let you achieve this standard before the time of passing. After they have passed, different story.