Here is something to consider with respect to doubles rankings. A player is at a tournament and guys are pairing up for doubles. An old friend, not quite at Player A's level, asks if Player A will team up with him. In a points system, if they earn no points, no harm done. In a head to head system, Player A has an incentive to be a snob about it and turn down the request. Not playing doubles at all is better for his ranking than playing and losing in the first round.
I love doubles, and precisely for that reason, I hope TRN does not do a doubles ranking. The unintended consequences could be destructive to the already underemphasized doubles aspect of junior tennis in the U.S.A.