Hey vinnye,
What a beast of a machine the Firebrand was. It actually saw no service in WW2, the Firebrand Mk.IV entering squadron service in September 1945. Your question is an interesting one, but remember they replaced the Sabre with the Bristol Centaurus in the TF.III model, even then the issues that plagued the aircraft did not entirely disappear. In service it was found to be good as neither a fighter nor a torpedo bomber. Pilots found it heavy to fly and difficult to land because the cockpit was closer to the tail than to the nos; engineers complained about its complexity and how difficult it was to maintain. It wasn't well liked in FAA service.
Even if the Sabre was replaced by either of the engines you suggest, the issues that plagued it would have still delayed its entry into service.