Obviously missing things:
1. Needs to fix keybindings, including setting readline shortcuts across all gui textfields. May be effectively impossible with so many gui toolkits floating around.
2. Needs a gui to manage configuration of startup items, login items.
3. Portable application distribution rather than futzing with installing a third party package source (may be effectively impossible for gui apps).
4. Cleaner systemd configuration tooling and especially documentation, even if it can't be expressed via a gui.
5. Cleaner process management.
6. Cleaner user management via GUI.
The look and feel mostly doesn't matter tbh; you'll just end up with something that looks like macos but still mostly functions like windows but without consistent keybindings or behavior or system management.