P.S. Yes, this would be a totally doable piece for many church choirs, in which case an organ is generally available. It's really common to have a general "keyboard" part and make the decision Sunday morning whether to use piano or organ based on the style of the piece, balance issues because of the number of singers who actually show up that morning, or even things as mundane as the organist needing to immediately launch into the Doxology at the end of the piece and having no time to walk from one instrument to the other. That means the organist is looking at a piano part and making their own editorial decisions about stops to use and where to put a bass line in the organ pedals, or the reverse, they are looking at an organ part, ignoring the stop settings and deciding how to add piano pedaling. Also lots of last minute changes to help the choir get their notes or to support the balance if, say, only one bass shows up to sing. Being a church organist is a specialized calling.