It sounds like you can use ghosting to do what you want. If you check Current on the Ghosting view next to Frames, it will draw a ghost on the current frame. If you have Auto Key turned off then the ghost won't update as you change the skeleton. Does that achieve your goal?
If working with auto key off is annoying, note that K is the Key Edited hotkey. It will key everything that has been changed. This is the same thing auto key does, except auto key does it all the time, as soon as you make any change, and the hotkey of course only does it when you press it.
