Depends on what you want the pivot to do.
Thing is the pivot is pretty easy to animate all you need to do is move 2 extra channels to the channelbox, but its pretty impossible to rig in a way that makes any sense because the datas so incomprehensible to most users*. Off course you can always do the same thing with 2 transforms if you wish. The only thing about this si that the rig is not necessarily intuitive to use.
However theres really few cases where you actually need to animate the pivot really. I mean you can animate the pivot if thats what you want to force out. But oftentimes you get a easier solution by not animating it and the exact same end result.
- it rarely make sense to animate the pivot back and forth in timeline as most user s loose grip on what they were doing after they move time back.
PS: The quetsion is a bit stupifd tough, your now forcing an answer to animate pivot whereas you dont really want to animate a pivot you want to get something done the simplest possible way. the fact that you THINK you need to animate the pivot is a titally different matter. Google for animating a rolling cube. (thing is tough a rolling cube ie easier to make by NOT animating the pivot)
