Two quick things to add.
One, alchemy (mentioned a while ago, and fairly integral to mysticism in medieval times). The quest for the Philosopher's Stone, as I hear it, wasn't to amass wealth. Sure, it could transmute lead to gold, but that wasn't the point - because having mastered the art of such transmutation, you could become immortal.
That was what they were after, and I've read records of one guy who claimed to have succeeded... although his claims were, of course, rather dodgy and difficult to prove so many centuries later.
Two, the whole thing about what to 'put in' to a game... arcane magic is a fairly touchy subject, but other than that, the point of such a Christian game would surely be to explore morality? Much like D&D, actually, although some people don't like the alignment rules. To enable an exploration of what's good and what's bad, you need access to all things, not just certain skills defined as 'good'. After all, what is good and why do
you get to define it?
I'll ask a theologian about mystic powers when he gets home, but I think the answers may surprise... oh, and I always defined magic as the application of knowledge; but Oxford says this:
The supposed art of influencing the course of events and of producing extraordinary physical phenomena by the occult control of nature or of spirits; sorcery, witchcraft. Also, the practice of this art.
Occult means 'not understood', very roughly, while sorcery is listed as the practice of magic or witchcraft, especially to cause harm. Useful fact for the day.