I really do like complexity, and that's rarely a good thing when designing game systems. I was definitely going down a complex path, and needed to re-think some things. I still want to use Threshold-Limited Magic, and base it off of the Power attribute. I'll use the following Threshold, Recovery and maximum mana/turn values:
| Power | Threshold | Recovery | Mana/turn |
| 1 | 0 | 0 | 0 |
| 2 | 0 | 0 | 0 |
| 3 | 1 | 1 | 0 |
| 4 | 3 | 1 | 0 |
| 5 | 5 | 2 | 0 |
| 6 | 7 | 2 | 0 |
| 7 | 9 | 3 | 0 |
| 8 | 12 | 4 | 0 |
| 9 | 16 | 5 | 0 |
| 10 | 20 | 7 | 0 |
| 11 | 24 | 8 | 1 |
| 12 | 28 | 10 | 3 |
| 13 | 33 | 11 | 4 |
| 14 | 39 | 13 | 6 |
| 15 | 45 | 15 | 8 |
| 16 | 51 | 17 | 10 |
| 17 | 57 | 19 | 12 |
| 18 | 64 | 22 | 15 |
| 19 | 72 | 24 | 17 |
| 20 | 80 | 27 | 20 |
These values are somewhat lower than standard Threshold Magic and I've capped how much can be channeled into a spell per turn. I'll start inherently magical races with Power above 10 (at 10, Max mana spent is 0, meaning you wouldn't be able to cast anything, but I will have powered magic items allow users to access their thresholds). Because they're all derived from Power, there's no need for the new advantages, but I may allow limitations.
I'll re-work the colleges using the portfolios covered by each god in the pantheon and assign a color. I may leave most spells as written and just change colleges and prerequisites. Skill levels could be based on either Logic or Creativity. I'm not sure how I want to do that yet. I may allow casters to choose, I may assign some spells to each attribute, or I may just pick one of the two attributes for all spells. Logic makes more sense if I want to have more "bookish" wizards, though creativity may work for making magic an art form (say for inherent D&D-style sorcerers or for bards).
Alternatively, I may make each color its own skill. And going that route, I could just use Path Magic, make each color a wildcard skill, or give each color a skill along with a verb (for example Transform and Brown could be combined to shape earth). I do still want magic to be somewhat slow, so Path Magic or a modified Syntactic Magic would fit there pretty nicely. Threshold still leaves the ability to use some major spells as a possibility. More to consider there.
For casters that that are not innately magical, they'll require tattoos to raise their Power attribute. I may provide a minor discount for that (say Limitation: Mana Tattoo, -20%). Spells would require mana from the color for its college. Say fire magic would require a red mana tattoo, and red mana would be limited by the size of the tattoo(s). In addition to the mana cost (that would increase threshold), there would always be a point of damage suffered by the caster (which would not apply to an inherently magic creature that does not use a tattoo; this would be part of the limitation reduction).
For casters that are innately magical, they can raise their Power attribute normally. This would only give them access to colleges they have innate access to (for instance, Elves will have access to Earth, Plant, Sun and Water magic, while Surface Dwarves may have access to Earth and Metal magic). If they wish to cast spells outside of those colleges, they would require a tattoo and raise their Power with the 20% limitation. For these spells, they would be subject to the same point of damage for casting.
Casters within a certain range of one another would all increase their threshold when using the same color of magic. This might require having a separate threshold for each color...which I really like, but may be too complex. But, I really like it. It's also 2am, which is usually when I start veering into more complexity. I'll think a little more on that.
So, this looks a little more concrete than my last brainstorm, but there are still some decisions to make. And so I don't forget, Adam suggested the idea of having casters able to diffuse spells by weaving another caster's spell back into a ley line. I REALLY like this idea, so I need to find a way to incorporate it. I've been basing a lot of ideas off of Brian Daley's Coramonde books, and distorting someone else's magic in that manner fits into the magic from that setting so well. There's a few other ideas that we discussed too, but some of those will be left for later.
I should probably add something here.
definitely like that idea of the diffusing, though wonder if it would work for all, or just users of same or cousin type aspects, or if someone for Change would be able to do it for all but others not as much? I'm not familiar with the books so not sure what your guys ideas are overall for that but like it
Some of the core concept is loosely based on material from the Coramonde books, but it's definitely divergent enough that I wouldn't consider it to be required reading.
I picture re-weaving as being specific to a specific color. A mage would have to first successfully identify the color of magic being used and successfully weave it back into a leyline. Misidentifying and re-weaving could have feedback consequences.