When rickey smiley was doing comicvieiw, his band was using the motif es, and the organ sounded very real when mixed with the other instruments
I play the Organ primarily. So when
I hear someone on a keyboard playing an Organ voice It's like...What in God's name are you doing?

But then again a Sax player would probably say the same thing if the guy on the keyboard played a Sax voice. Because he knows the sound of the instrument.
BUT.
MOST people can't really tell and don't really CARE. My wife and I visited a church on Friday and we were in the Balcony. We couldn't see the musicians. They started playing and my wife looked at me and said "They have an Organ". I said "No they don't".

It was a Motif XS8 (and the Organ voice was believable).
So as long as you're not playing for the musicians but the congregation, you can definitely get away with it...I'd rather not do it, but you can get away with it.