Just a side note here: the spell adders and multipliers are not necessarily realm-specific. A few are not specific at all, and some are profession-specific. I appreciate the logic for the interpretation of what power points are (even though I still think different mechanisms would be preferable), but the magic items by themselves are not a proof of this
I agree that different mechanisms would be nice, but at least you can interpret the existing common mechanic in different ways without feeling like you're making absurd assertions and justifications to get to the goal of having them be distinct in some way. And yes, some items can handle all realms but they are more rare and difficulty to make. There are hybrid and profession specific items but there are also swords of slaying against specific types of foes, so that just proves that alchemists can be creative in adding specific restrictions on items and using those to offset other factors in the item creation.
Interesting variation as well. When I dish out spell enhancers, they tend to be profession-specific. Realm-specific are rarer, and universal enhancers are even rarers. Simply because the more restrictions there are, the easier it is to build a significant item.
In my view, magic item creation is not an industry - you do not produce hoping that someone will buy. It is always built on purpose (build-on-demand). As such, there is no reason to make something that is not profession-specific unless the customer explicitly mentions that the variability is required. Since most orders are "for personal use", customers know what to order. Ideally, they would probably require something even more specific ("usable only by me and those of my blood", or something like that), but technically, this is not a restriction anymore but a protection of sorts, and as such costs extra
[the consequence of that choice is, of course, that a significant number of items the characters discover or loot are items they cannot use, because they were made for people like the ones they just killed, which does not necessarily coincide with what they are. The character usually end up having a very secret cache full of items usable by necromancers, evil priests, and the like, with a big metaphorical "danger - radiation" sign on the door
Or they give them to a Loremaster they know for 'safekeeping' (or dumping in the nearest volcano)].
But I think we are drifting away from the main topic. Sorry.
Back on track : in my current variation, I still use generic Power Points, but there is a possibility for casters to gain extra power by 'gathering Essaence' instead of using one's one PP. This option is not available to Mentalism users. Essence and Channeling users can use it, but the mechanisms are different for both and the side effects for failure are also different for both (it's a one-or-the-other choice: either you use ambient Essaence, or you use your own, but you cannot mix both). The Essaence method tends to be slower. The Channeling method tends to be more dangerous the more often you use it. Both increase in difficulty with the number of PPs required.
There is also a possibility (universal, in this case) to use life energy to power magic when a caster has no PP left. This basically provides PP at the cost of progressively more severe burnout (damage).
This is derived from my personal take on Shadow World cosmology and its impact on magic: Channeling users do not channel power from their chosen God all the time. Most of the time, they use their own magical capability, with a psychological symbolism that 'enables' their magic. The God is aware of the use of the symbol and can choose to block (or enhance) the user's magic, but they seldom do so. Use of divine power to perform magic requires actual use of the Channeling skill (which is basically the 'gather Essaence' for Channelers as explained above).
Channelers can function without a patron god, as long as they believe in *something* (the symbol is what enables their mind to work the manipulation of Essaence). Basically, all magic users use the same power source - which is why Arcane exists - it is magic before the various crutches were invented.
This might end up becoming different casting systems if and when I refine my hack further, of course. I would like to go even further and provide system variations for different *traditions* of magic, but, well, time is not on my side