I would love it if the Undo request gave some indication of the affected action(s).
In a game last night I had an opponent play a Plaza then request an Undo. The last thing in the game log was "X draws a card" (paraphrasing).
It's not clear if they wanted to undo the Plaza play or simply the decision to discard a treasure card, because the latter isn't shown in the log.
I would love to get a message that says something like: "X wishes to undo the decision: Discard treasure (Plaza)".
At the very least, I would want one piece of information in the undo request: whether or not any new information was revealed since before the action was taken that they want to undo.