I have a function that I've aliased `ssh` to that does a similar thing, so my default is to have tmux running on the remote.

It checks if the remote has tmux first though:

    function ssht() {
      /usr/bin/ssh -t "$@" "which tmux 2>&1 > /dev/null && tmux -u -CC new -A -s default"
    }
    alias ssh=ssht