Hi,
So, there's a sidebar in Hedge Magic, in the chapter about the Vitkir, about Odin's Sacrifice. It shows an extreme method a person can either gain the Gift (!!) or open the Runes. Can Hermetic Magi do this? And can they use Initiations to learn other Hedge virtues?
E.
I think the sidebar you refer to mentions what the Vitkir Gift initiation will do if your gift is already open, but I don't have my copy in front of me.
I can't think of any reason a Hermetic Magi couldn't go through a Hedge Initiation; in a sense, all initiations can be undertaken by anyone. However, if the virtue given is only compatible with a Hedge Tradition/Gift, then the initiation will do the Hermetic Magi no real good. (Similar to how the inner mystery initiations of the Mystery Cult houses wouldn't do a non-gifted person any good.)
It is noted that if you are opened to Hermetic magic, in the Integration portion, that if you undergo Odin's sacrifice, then you immediately get a Discovery towards integrating Vitkir runes, but no, they cannot be opened because their gift is already open. Alternatively, they might get a major virtue because their gift is already opened.
If the magus gets his gift opened a second time by a mystagogue master, then the mystagogue needs to have some 100+ opening lab total to be able to do so, since the arts are added against it. However, if the hermetic magus was opened subtly, then he can likely be opened just about everywhere (especially if it's all subtle).
People seem overly fond of forgetting what Initiation is for. Virtues explicitly can be taught; the core rules state this. Initiation allows you to avoid the massive penalties due to your existing Arts and Virtues.
As such, you clearly can be Initiated by the intent of the original rules. What you could not do is use combinations of the different magics since they're not integrated. An Hermetic/Vitkir could use the Hermetic Arts and use the Runes, but couldn't use the one as part of the other - no Perdo Berkana or Thurisaz Animal (examples are utterly at random and not expected to mean anything).
Yes, this potentially allows a magus to acquire obscene potential power. At the price of being a virtual slave for multiple mystagogues and masters, never having time to actually study anything, and being crippled by many Flaws and Ordeals. I see no problem here. Sacrificing power and life for potential power is good for stories and mostly bad for magi.