Hello Troyf, and thanks a lot for sharing this solution - it looks very promising!
I have an update about another approach that's supposed to work, according to an Apple representative that I had a long digital chat with. She told me that during the update of Mac OS to Catalina, it will also install all the iWork apps that are compatible with the new Mac OS. I asked her specifically if the iWork apps were built into the installer, and she replied that was correct, but I'd need a strong and stable WiFi or cable connection.
Unfortunately my only internet connection is through a cell phone network, which has reasonable speeds but maxes out at 3 GB per day! Her comment to that was: "That might not work." During a recent bit of travel I'd made a point of downloading a Catalina installer, which weighs in at 8.1 GB.
It sounds like her claim is contradicted by your experience of upgrading to Catalina, since you didn't automatically end up with the iWork apps installed after the upgrade. Maybe some methods of invoking the upgrade would work while others wouldn't, but she didn't give any particular instructions for this, other than insuring a good internet connection. She also said that some installers would include all the needed files, while others would need to download things.
Since arranging for a strong and stable internet connection for a day would involve a lot of delays and effort, I'm going to try a clean installation from the installer I have, and see what I end up with. I'll do this on a blank partition, to avoid any risk to my working bootable partition. I've also installed my iWork '09 apps into the virtual machine I've already got for running Snow Leopard (Mac OS 10.6.8).