Using ImageBuilder with a snapshot

I am hoping to use ImageBuilder to be able to flash a large number of devices (25+) with a custom file server setup. I have never tried to use this tool before, and a have a question about using it for a RavPower RP-WD009. As of 7/12/2020, the device is only supported by a snapshot, and the 'install' firmware and 'upgrade' firmware snapshots do not contain the same content. The install firmware does not support many common packages that I need like LUCI (it complains about a kernel dependency). The upgrade firmware does support the packages that I need to use.

What is the best way to build an image to flash devices running factory firmware while incorporating support added from the upgrade firmware?