Forst, a general show of what I consider an OPTIMIZED FIGHTER COMPANION in my real world sagas. Mateu de Besalú, Knight Hospitallier - development. It was created for the Light of Andorra saga, that is high power and basically makes everybody Wealthy during character creation, but that is it. He has 4 virtues and flaws, and a further virtue in the form of a +2 attack and defense sword. That might help you understand some of my hesitations.
Basically the problems I see is with getting a whole bunch of supernatural abilities easily. Or not that easily, but getting them anyway. Opening the Gift grants you something in the scale of +10 to +20 virtues for free, and changes completely the focus and capabilities of the character. Same if you can go around initiating supernatural virtues for no cost.
The forest paths and other initiations that require heavy costs for the characters I find to be quite OK (without having played them ever, mind you, so this might not be true in real gaming).
So maybe what I am doing here is putting a ban on Opening the Gift or Acquiring Virtues without a corresponding equal level flaw. Your core character is that, your core. If you are a priest of Arduinna, or an Ars Notoria franciscan that is what you are it is not a "level 1 character" that will raise to level 10 branching into other D&D classes. You can get more virtues and flaws, but you are not getting initiated and BAM! suddenly you also are a Gifted Natural Magician, an Amazon or a Gruagach.
The initial characters that you are creating are far from useless. More than 2 went all the way to get a +9 (plus characteristic) in non accelerated abilities. I am not overly concerned about that, but this is the focus of your character, and I expect it to remain the focus of your character for the saga.
Learning abilities that make no background sense (Wilhelm, I am looking at you and your Mechanica for a necromancer) is also extremely discouraged. And it would have a heavy cost as well. Maybe focusing on material beings diminishes your connection to the dead, dunno.
So, if you want initiations, they will follow the lines of Initiations for Ungifted characters or forest paths. They will come at a cost. I think this is thematic to the approach of the saga and I do not feel that it substracts heavily from what I expect from the characters.
Initiations are well and good. Free virtues and character swaps not so much.
I hope you understand what I am saying and it makes sense to you.