the very fact that i named steamos as target is steam-runtime which will be very easy to replicate in future sandboxed applications. if it runs trough steam on steamos. even now, without sandoboxing any distro could simply modify run.sh from steam and have perfect compatibility. goal achieved in 2 min
what you're mistaking here is the fact you're proclaiming i'm proposing default workstation target, which i am not. i'm proposing test target for bug reporting. if it works on setup like this there won't be "ubuntu x.y morning version supported only", but rather "linux supported". sometimes i just hate ubuntu users and their inflexibility to understand
let's see. they deviate in desktop notifications, they deviate in how menu is handled, in future they'll move to Mir, rest to wayland, systemd support is not comming until 16. ubuntu runs its own unique DE which doesn't really work like others (well, so isn't gnome in that aspect, so this is a bit moot), shall i go on?