I find it better not to use things like XDM and just prefer to startx with an ~/.xinitrc. If a crash happens with X, I can either use alt F2 (or F3, F4 etc) to get to a log in prompt. If that is locked, always have SSHD running so you can SSH in and run top to see the issue and kill that PID.I'm really hoping Wayland will fix the issue of "display server goes down, so does everything you had open", but, I have no idea, I haven't tried it. IIRC POSIX specifies that all child programs have to end execution when the parent ends execution, so, if that's the case, I'm worried Wayland will act the same. Again, haven't tried it, been meaning to. If they fixed the fucking display server taking all your applications down with it that would be a huge plus.
Crashes are incredibly rare for me and tend to happen on a fresh install where I've yet to get everything set up perfectly.