Can you? Yes... Should you? well.... remember that the fire control group consists of the hammer, the sear and the disconnector. Most folks will suggest that you get a "matched" set... where all of the parts are designed to fit... some are pre-matched so that everything works like a "trigger job"
The only way you would know is to try to replace the hammer, but be very sensitive to determine if it deteriorates the quality of the trigger... pull and creep. If you have a problem be prepared to replace the original... or be sure you can get the matching sear and disconnector.
Well i haven't decided on whether or not I am going to get a pt1911, The one I've handled seems like a well built 1911, it's that lock I'm not too thrilled with. I switched hammers out on my other 1911 because I had to put a beaver tail gripsafety on it, the hammer bite was bad on that thing.