I feel a little munchkin-like for even looking at this but it feels like there should be some way to get in game synergy from the closely connected ideas of Numerology, Germatia, and Kabbalah - looking for wisdom and power in the numerical analysis of a text. BTW, I know I'm being long winded as I talk through the idea.
Germatia has a couple of interesting things for a Hermetic Magus in game terms. It is divine aligned which is nice, it can provide an effect similar to a limited longevity potion when combined with Understanding, and with Understanding it can provide divination like effects. Nothing stunning but interesting. Kabbalah is similar. It is connected to the Wonders power which is sort of generic spellcasting/miracles but if you are good enough you can create a golem which is a neat effect.
They both have some big drawbacks in game mechanical terms. Even for just one method and one power you need six virtue points and a bunch of XP. You could find a way to initiate it after character creation but it is still a huge XP drain to get useful effects plus the initiation might end up limiting all of your magic.
Hermetic Numerology is similar to Kabbalah. Use your understanding of a text / the numerology in the text to boost or cast magic. Germatia is somewhat similar to Divination (numerology). Both of the Jewish traditions have the useful divine aura connection but otherwise the interesting things are the Shinnue Shem ritual and the ability to create a Golem.
From the point of view of a Hermetic Magus (not a Holy mage) it feels like these make great ideas for breakthroughts. The Bjornaer already have part of the idea of the Shinnue Shem ritual in their mysteries (I would assume that this is a parallel development not cross fertilization of the idea) but a no vis effect similar to a longevity ritual that could be done on non-magi without fertility effects would be pretty good. Golem creation would also be pretty great (creating life and granting it power!) although it feels like a bigger breakthrough to make a Hermetic version since the creation of life is so tied to the Divine.
So the question becomes are these minor or major breakthroughs? Can a Golem ever be created by Hermetic magic or is that purely the realm of the Divine? Is there any reason that a Hermetic magus who knew of these two applications of Jewish holy mysticism (from a background, from in game time with a Kabbalist, or from a book) couldn't work on these are breakthroughs?
Perhaps the biggest question; if a character knew Hermetic Numerology and Divination (numerology) could they work on a breakthrough (or initiation) to use holy texts to align their numerology and divination effects with divine and magical auras or is that something that is only in the realm of initiating the Holy Magus virtue? The reason I ask is that there is a note that Kabbalists rarely have True Faith which implies that their magic is divine because they are using divine texts.
Finally, to bring things full circle, this is all inspired by the mental leap my mind made while looking at Bjornaer Clan Sirnas and their role as protectors and the role of a Kabbalist and Golem as protectors. Weird mental leaps for the win!