People have jokingly said that Admiral Piet replaces officers that Darth Vader kills. Based on the Chimaera's ability to have a "side board" of Fleet Command cards, I can see Piet working just this way. The Imperial player can remove her Commander and put Admiral Piet into play. (Removed Commander gives the opponent points equal to the card value?) Emperor Palpatine and Darth Vader probably can't be removed.

Of course, cards that aren't in play can't be used, so you need another card to trigger this ability. The Admiral Piet officer card? Or the Darth Vader officer card??? The officer version of Admiral Piet would be removed from play (at no cost) when the commander version is substituted in.