Personally, I don’t see the need for this with NixOS. Setting aside the fact that Omarchy is way too opinionated (Basecamp installed by default?), NixOS is already quite composable, so you can easily build a well-formed experience out of isolated NixOS modules.
Why? Most people’s system configurations are publicly accessible on GitHub. Stuff like Omarchy only makes sense* when the system must be configured imperatively and there is a cost to trying things (accumulation of application residue). When you build your system declaratively you can just copy the bits you like from other people’s configs, or even just run their config as-is.
* IMO Omarchy doesn’t make sense anyway, far too much opinion and too little utility. It’s not a distro it’s some guy’s overly promoted pile of crufty scripts and dotfiles.
Personally, I don’t see the need for this with NixOS. Setting aside the fact that Omarchy is way too opinionated (Basecamp installed by default?), NixOS is already quite composable, so you can easily build a well-formed experience out of isolated NixOS modules.