So Crossover 16.2.0 doesn't work; but a nightly build 20170508 does. Ill be trying other nightly build till 16.3 comes out.
1) Download the 4 install packages from the official FF XI site: http://www.playonline.com/ff11us/download/media/install_win.html
2) If you haven't created a windows 10 bottle do so. Don't do the game install via the install wizard it will just fail (even though it has worked in the past)
3) Install via right click into the bottle Core Fonts, and .net framework 4
4) Right click on the bottle again and run command. Brows to drive_c/windows folder then explorer.exe and Run.
5) Navigate to your FF XI installer and right click on it then open. I found it best to copy the installer to your bottle drive_c area first.
Everything should install like normal and run just fine. The first installation after the Playonline installation took forever but eventually kicks off and the rest installs rather quickly.