Must have

Button component which runs a command on click
This would allow to create boot options to boot e.g. into bios or dual boot from greeter

Nice to have

Animations for windows
Either "hardcode" some animation keyframes or add option to add delay before closing to animate the close (add css class in this time)
Support for fingerprint readers with fprint and facial recognition login with howdy
A layout subcommand which prints the layout tree