Hi there. I tried a couple of times to install elive among these 11 or so years away. Got troubles with X in different machines (live version). Yesterday I got problems with multiple screens, and got the black screen 
. Luckily i installed e16 (love the waves effect and miss it!!!). so i managed myself to kill X in tty2 and somehow got to login screen with WM selector. My suggestion is to add a script to reconfigure X from console while offline (dpkg-reconfigure Xorg was the command in ubuntuā¦ pfff this gets me to the my good old times 
). i canāt remember bash scripting but something like "| if grep āXserver Fatal Errorā = true show āUse the following command to configure blablablaā. Searched in the forums back in those years and couldnāt find an answer in the old forum (should I asked?). Thana if you read this, freenode misses you 
grep (EE) /var/log/Xorg.0.log
grep -> program to find a pattern in a file
(EE) - > what should grep search for? Because () are special characters, they should be escaped by
/var/log/Xorg.0.log -> the File that should be looked in.
If the ERROR (EE) donāt get any result, try WARNING (WW), too.
And then weāve got the ~/.xsession-errors ā¦ Try to read it from down to up. But I donāt know what to search for here.
Back in the old days (Debian 2.2 āPotatoā for me), often ācat /var/log/Xorg.0.log | grep (EE)ā is used. But this is known as āuseless use of catā. Because grep is reading the content from STDIN as well as from the file direct.
for willys (the OP)
Have you tried editing the xorg.conf file in /etc? There is an expression that Real men edit their xorg.conf by hand (instead of letting a utility fix it) . Open a terminal and view the .xsession errors there, while another terminal is where you make the necessary repairs using your preferred editor.
I did a LOT of this when I had an nvidia-equipped desktop that had two screens. This was way before enlightenment made it easier.
Hahha 
Mmmh, the X11 startup has a "multiple different attempts" feature (trying with vesa, trying with no-ecore-vsync, etc...) options, which are not much tested but they are meant to work, in the end, it suggest to start a shell in failed cases
In other words, with this "auto" configurator should not be needed a configurator and it should manage it better, which they are very delicated (not always compatible). By other side it has not been tested much (not easy to simulate a "failed with intel, try with vesa" state but it should generate the configurations correctly by itself, see also this screenshot: