I also have an extreme degree of toe-out. There's a few things I'd like to add to this thread.

Speedplay have 15 degrees of float, and the cleat cannot be rotated on the shoe. This allows for 7.5 degrees of float right, and 7.5 degrees of float to the left - period. This is not even close to enough for my right foot's roughly 16 degrees of toe-out.

I also use a kneesaver pedal extender on the right side. I also twist my Shimano cleat to the maximum, and use the new Shimano shoes with the long 3-hole cleat slots to get even more rotation out of the shoe. This plus the 6 degrees of float on the yellow cleats allow me to get to the 16 degrees I need.