I have updated my netinstall project to include the new "mode script", and other things. In particular, a more friendly mknetinstall "wizard" around the project's Makefile that does all the package downloading stuff automatically and starts netinstall-cli with options based on ENV vars. And RouterOS container install script was updated, too (name vs list).
For device-mode, the default logic is to always set device-mode (in 7.22 or greater) to mode=advanced, and if container or zerotier are selected, the those get added as =yes automatically. There is a MODESCRIPT env var that takes the particular command you want to use to override this however.
And I tested the new mode-script itself with netinstall-cli and works as expected. Multiple netinstalls on ARM, ARM64, MMIPS, and MIPSBE, all seem to work okay. Both my script and netinstall-cli's new -sm "mode script" option.
It's on GitHub, with the container version for RouterOS on DockerHub.
Anyway, the "mode script" solves my complaints. So thanks.