Dont be an "Ice Road Trucker" If you learn to fly in the KF you will not know any difference, but your feet will be much more agile when you move into another airplane. Many Many people have built and learned to fly in the Avid or Kitfox line of aircraft. That was a major portion of the original intent of the design. During original conception it was not to allow older pilots who could not pass a physical anymore to transition into a light aircraft..

Saying that you should learn to fly in different plane first is like saying all drivers should only learn to drive using an automatic tranny, and later in your life you can learn to drive a stick shift.