I also believe to know some stuff about the PS rune system by now. The explanation I gave was greatly simplified because the links provide it in greater detail anyway.
I don\'t know about the combinations of glyphs, but I\'d rather gor for a \"charge intensity\" for each glyph or glyph combo that you can freely select. The combination of glyphs will define the spell, no single glyph will IMO represent \"the spell as such\", unless it\'s a one-glyph spell. Even if it is, the same glyph can appear in other spells at different locations as well.
Glyphs _might_ represent spell properties, like fire / water / whatever but I doubt it. There might be blocks of glyphs representing spell attibutes. These blocks could be charged to any extent by your wish. The overall power might also be a combo. This way, you could, by simply varying the attributes, change the fireball spell into a ice explosion spell. If you know how to handle these elements, that is.
The charge level could also be set to more zhan 100%, overcharging the spell. Doing this for the overall power will of course be the most risky thing, but overcharging the individual attributes will make them unstable as well. If you overcharge fire and earth, you might end up having a powerful volcano spell, but also fire could break down and you\'re left with a heap of dirt, or whatever.
Undercharging will make the whole thing easier to control, but still your skill is important. Undercharged spells will, natrally, drain less mana and be less powerful.
The end result has been called \"k-factor\", which is very much like (no, even more natural) the P&P system\'s rules, isn\'t it? THAC0, for example.

Also, as for the \"number v.s. skill\": \"skill\" _is_ a number. Whether it is actually being displayed or not is entirely irrelevant. For the devs it\'s going to be a number, for the player it\'s a skill, because it\'s what\'s they deal with from their particular environment\'s point of view.
Perhaps we could base the internal rule representation on fuzzy logic. This would yield greater flexibility and closer resemble real-world rules. It hasn\'t been tried for RPGs, but it might be good, albeit much work.