[Thaumatology...sorta] Elemental magic system

[CarrotandStick]

So. I'm working on a GURPS setting based on the venerable Secret of Mana game series.
This setting comes with its own quirks and specifics, such as an 8-element magic system. For those not familiar, the elements are Fire, Earth, Wind, Water, Moon, Leaf, Light and Dark.
The question is, how to construct the magic system?
I had thought to use Bang! skills or the domain based option in Thaumatology the name of which I forget (at work, book not in front of me) for each of the elements use the threshold charts for effect. I had a few questions though.

1) Which makes more sense to you? An increasing scale for the elemental skills (4,8,16, etc) or a flat scale (10/level, for example)?

2) How does this alternate magic system handle non-direct spells? I had thought to make Moon abstract concepts and change, Light positive effect and Dark negative effect with the usual elemental connotations. For example, to create lust one would spell Moon (concepts, perceptions) with streaks of Fire (passion, etc). However, the threshold charts seem to only deal with physical, tangible effects. How would you calculate this? Also, would you make the player roll versus his higher or lower for a combined spell?

3) The charts state that if your skill in a domain is 15 and you roll a 12, you can use up to level 3 (threshold) on the charts. All the charts. Is this balanced? What if you made the levels cheaper but you got points to distribute on the charts equal to threshold?
Example: Casting a fireball. Fire skill 15, rolls 12. Three threshold.
Default: Resulting fireball has 3 on Range, 3 on Duration, 3 on Damage, etc.
Possible: Caster has three points to distribute above the default of 1. Makes range 2 (1 point), Damage 2 (1 point) and Duration 2 (1 point). All other tables will read as the level 1 entry.

[Refplace]

The Domain system is flat based cost with the levels broken up into how many you want and the effect based on that.
The name for it is Realm based magic.
You could also do this with Syntactic, words, or the Ritual magic system pretty easily. Each has its own flavor.

[shivafang]

Given the limited number of spells in each element for Secret of Mana, I'd go with a Powers system with each element having it's own Talent Level.

[CarrotandStick]

Originally Posted by shivafang

Given the limited number of spells in each element for Secret of Mana, I'd go with a Powers system with each element having it's own Talent Level.

I wanted to avoid the game's magic system entirely. It's simplistic, combat focused, and for a game system with the available depth of GURPS, a crying shame.