orthogonal shadow magic?

[Violet Octopus]

So a while back Maerok posted a fix for the shadowcaster, called theshadowheart, essentially the sorcerer's casting with the shadowcaster's mystery list.
This is good if there are no other spontaneous caster classes (including sorcerer), as it gives a nice mechanical difference between shadow and standard magic. But the campaign I want to run will have spontaneous casters, so I need something different.
So I thought of the following, and would like people's input as to whether it's workable.

Orthogonal Shadow Magic:
A shadowcaster learns 1 mystery/level as normal, without having to know prior mysteries in the same path. Each mystery is usable twice per day, except that these mystery uses are shared with other mysteries on the same path.
So a 3rd level shadowcaster might know Steel Shadows, from the Cloak of Shadows path (usable twice/day) and Life Fades and Flesh Fails from the Touch of Twilight path (usable a total of 4 times/day).

I haven't figured out whether this shadowcaster would get bonus feats for completing paths (increased flexibility is already an incentive), or whether they'd get bonus mysteries/day for a high casting stat and how that would work. And the uses/day and spells known are all up for changes.

So...thoughts?

[Suzuro]

This would put a huge disadvantage on people who choose to specialize in a single path. For instance, if they really like the flavor of one path or something, but then they only get two uses for the entire path.

-Suzuro