Many distros have meta-packages, which install a specific desktop and some good defaults.

Omarchy could have just been two packages, omarchy-defaults (a package containing the default configs) and omarchy-base (a metapackage depending on all the packages omarchy would want to install by default).

Then you could just use a regular arch setup, and set it to install omarchy-base, and you'd get the same end result, but you could also sidegrade between regular arch and the omarchy configs.

See e.g. https://wiki.debian.org/DebianDesktop/Tasks