Okay, so it is well established that mounts/riders do not confer evasion from one to the other. That's fine to me and (as I have now discussed this with them) my group. We would, however, find some way to make this possible.

Discussing things with the primary GM, we are wanting to craft a feat that (with a clever use of the Ride skill) allowed the mount to confer evasion to its rider.

Something like this:
Skilled Rider
Prerequisite: 7 ranks in Ride, Mounted Combat
Benefit: By succeeding on a Ride check (DC = 10 + 1/2 damage taken) a rider may gain the benefit of Evasion if your mount has Evasion.
Normal: A rider does not gain the benefits of Evasion from his mount.
Just a rough stab at a feat. I'm sure it needs a lot of polishing. Also, maybe their needs to be a "greater" version that allows Improved Evasion.

Thoughts?