I asked them about it and here is what they said:
"Kinesis will not make a custom version of the Advantage Keyboard, sorry.
With the Advantage keyboard, Red Cherry would not be a good fit, since it is a linear switch, and part of the benefit of using Cherry switches on that model is the tactile and audible feedback.
Also, at the moment, we do not have any keyboards with a Red Cherry switch, and do not anticipate they will be available on any of our current offerings soon.
Thank you for visiting our website, if you have any further questions please feel free to contact me.......Randy"