Can I pose a theory? Could it be that the Vex plan is to replicate a Hive God? I just read up some Grimoire and it looked like basically, Oryx told Quria that he would need thousands of systems worth of power to replicate him, and after that Quria sent all that info, plus everything he knew of Oryx, to the higher Vex Minds. Maybe the Vex need all those machine planets so they can form their own version of a Hive God based on that information, using the Black Gardens heart as a supplement for Oryx's worm, and the Sol Progeny as their link to it?