Through nix-env it even already has the idea (albeit discouraged) of imperative package management like apt.
Having spent a while with NixOS, running containers for user applications seems like using a cannon to kill a fly. The 'simple' alternative is to drop FHS altogether - which containerization is kind of doing in a roundabout way by isolating the app filesystem from system fhs.
As for it being for developers only... I get that perspective. Debian/Ubuntu packaging is also hard, AUR packaging has its quirks. A lot of this is hidden behind the package manager, wheras with NixOS it is more obvious.
The killer idea for NixOS would be to make package management for Joe Q Public as easy to use as apt while. Tools like MyNixOS[1] are emerging which might bridge that gap.
