Here how I see the problem of the current colorwheel problem and why I think the triangle within a circle fixes it.
The current design basically implements the HSV color model. Only, and here's the problem, in reduced mode you can only adjust H and S. Where's the V? In reduced mode, you can not select all possible colors.
The triangle within a circle gives you access to the V component as well. This makes it possible to select any color you want right from the reduced mode screen.
Of course, I'm all in support of adding the alpha slider to the reduced mode!