I doubt the arm rods were removeable. As I understand it, most removeable arm rods don't perform the way puppeteers prefer. Most likely, since there were several puppets of each character made, there were probably some without arm rods. Frequently the puppets had heads that were detachable from the bodies, so some bodies were probably specially made to do different things. Frequently you see Jim holding the Kermit whose body has no legs, but then there's the Kermit that they used to sit on the wall and talk to the guest star. I always assumed that these legs just velcroed on or something, but I noticed on one episode that you can see how the leg continues over the wall, behind kermit, and I assume there is a control back there to make his legs move, kick etc....
As someone who grew up coveting a real live Muppet puppet (even a decent stuffed version) it was hard to imagine that these people who worked with the real Muppets might even have multiple copies of one character. I mean, I know that that's what they do, they build puppets, but the ones you saw on the screen were such works of art, that to think that they had captured this magic, and cranked out half a dozen Gonzo's, Piggy's, or Fozzies, was just unfathomable.
What was your question?