Comment by cwel

The issue in your setup is Windows^tm. (what I do) gaming machine's shell profile,

  if [[ $(tty) == "/dev/tty2" ]]; then
  <insert your steamOS session invocation/args here>; sudo chvt 1; exit
  fi

then all you need is some event(s) to trigger changing to tty2 on the target machine. perhaps when a controller connects, or your tv changes input, or you press a button on your tv/tv box remote.