This is just my throwing every idea out there to see if anything sticks. There may be mechanic misunderstadings, but hopefully not.
Accurate bolt- Seems a little underpowered since shapes provide the same effect with IMO more utility. My idea would have it be a prerequisite for a new edge. So what would tie in with it well?
(Stable Bolt: Increases your bolt's minimum damage up to 2 points) per rank. For example I believe the base is 2-3 damage, 1 charge would be 4-6, with this edge is would be base 3-3, 1 charge 6-6
Fun with shapes- Some more with prerequisite edge ideas,
Quick shape (req 2 shapes): For an additional energy cost, instantly fire another shape. I feel this would give more use to ball/wave, but also provide more reason for taking multiple shapes. For example you have ball equipped and an enemy surprises you when you move around a corner, instead of eating your own damage you could pay +? energy and fire another shape.
Shape mastery: Taking additional "ranks" in a shape you already have would make its size as if it was 1 charge level higher. For bolt/normal shape a possibility could be penetrating 1 enemy per rank.
Chose your default spell set- While inversion is easy to get I think it would be fun to pick which set of spells is your default. If you were 'A' set, inversion would make you 'B', if you were 'B' inversion would make you 'A'.
And finally to make Mage a little more viable, I would suggest a way to exchange spellpoints for edge points. For evenness either 3 to 1 or 5 to 1.


I definitely like the Stable Bolt edge, and the various shape edges. I'm not sure when more new content stuff will go in MG, possibly at 2.5, but when it does, look for some version of these to be in it.
The inversion thing is probably not going in, due to the havoc it would wreak in a couple places in the code. It would also probably require some new titles, to avoid the weird situation where you're a Light mage, not inverted, and yet your spells curse and harm your enemies (i.e., if you select the "base inverted" option your title is "Twisted Heliomancer" or whatever).
To be perfectly honest, I never expected anyone to actually complete the game with the Mage title. I would, in fact, consider it a pretty serious failure of difficulty if it were not very hard to pull off a raw Mage win. I'm absolutely content to leave it as a sort of "challenge mode".