For production environment?

Is there someone internally that is capable, and willing to support it?

do they expect vendor support as well?

For business, especially one where you dont want to be "that person" they call for tech support randomly and you would rather direct them to the vendor indeed I agree set them up with a Synology build and enjoy your free time

If you are their IT person, maaaybe a custom build would work, but how long do you plan to stay and consider how troubleshooting that device will go, or the lack of vendor support where you are limited to vendors supporting each individual part as opposed to the hardware and software as a whole.

Also consider how well off your client will be with said hardware if you move on and someone else has to support it. You will likely be setting them up for failure at most, and headaches at a minimum. It will be referred to as "that custom build some dude made but nobody knows anything about" and will likely direct the church towards buying a proper business/enterprise solution to replace it after trouble they struggle to support it anyways