@Coin
Interesting idea.
Over lunch, I devised an alternative to what I proposed before: a custom-design "Avatar" built around one Power attribute, one Finesse attribute, and one Resistance attribute. The Avatar is the PC's conception of his idealized self as Imago, and defines how his magic is formed and manifested. The PC's Arcana are limited to the PC's sum of Avatar attribute points, divided by 3 and rounded down.
Example: Ganymede's Avatar is the embodiment of Pedantry, where all aspects of reality may be shifted based on one's mental will, knowledge, and acumen. The Avatar therefore is based on Intelligence, Wits, and Resolve. Out of CGen, she picks Intelligence 4 (because she's stupidly smarter than you, stupid), Wits 2, and Resolve 2. She elects to take 4 XP from her CGen-awarded XP to take Intelligence 5, because daayyyyyyum, she be the smartest bitch queen, bitch. The total of her Avatar attributes is 9, so she can start with any Arcana at 3.
Next, Rotes are highly personal, and developed through repeated reiterations of the Imago. The thing is, how the Imago is formed is affected by a Mage's Avatar. When developing the Rote, the Mage has to describe how the Imago is formed, and then propose an applicable attribute and skill and Arcana modifier. The attribute chosen must be one of the Avatar attributes, and bear a reasonable relationship to the Imago and effect; the skill chosen must be reasonably-related to what the Mage must do to cast the spell (e.g., if you have to strike the target with your hand, then Brawl); and, as expected, the Arcana must be the highest level Arcana necessary for the Rote, or, if there are two or more of the same, one of those.
Example: Ganymede conceives of a Rote that would allow her to muddle and bewilder a target after delivering a sentence of impenetrable logic and complexity. She proposes the roll to be Intelligence + Empathy + Mind. EmmahSue, who reviews the Rote, disagrees with the use of Empathy, and instead proposes that Persuasion be used. Ganymede, not wanting to mentally beat up poor EmmahSue, who, after all, has to deal with Mr. Raptor, accepts. Hence, the creation of the Rote: "Ganymede's Baffling Balderdash."
To add a layer of understandable complexity -- and to restrict the circle-jerking of rote-swapping -- suppose that a Mage can only use Rotes that use his Avatar's attributes. That means that "Ganymede's Baffling Balderdash" can only be used by Mages whose Avatars have Intelligence as the Power attribute.
Buuuuut, suppose we make the game a little more interesting by awarding players that teach and Rotes beats, which slightly reduce costs. Then people would have an incentive to mix and mingle, get into tutelage agreements, and, you know, role-play.
Just some thoughts.