[Michael Cule]

I'm also thinking of using this as part of a 'school of magic' setting where the pupils enter as Mage-O and earn their higher magic by an initiation that realises the Magery-1 (RPM) or Magery-1 (Threshold Magic) or whatever.

There might be one or two Archmages who have the ability to use more than one sort of magic... But I'd make it a Bad Idea, possibly with the risk of death if you try to initiate to two different ways of doing things.