hmmm, 3 zone hihat... never thought of it!
Though I wouldn't necessarely want to have switches on my hihat : hitting a switch is not exactly like hitting a regular cymbal. I'm sure I'd loose some important sensibility (especially with soft notes).
Like I already said, this design works great, but I do have to use a little more strenght to trigger the switches.
I can't really figure if a 3-zone Yamaha design on a hihat would be compatible with both MD and any drum software. For instance, I dont think you could control a 3rd note with your pedal in BFD2.