Still interested in this. At this point, I’ve purchased 5x AR750S, and 3x GL-X750 with the hopes of building out a distributed mesh with LTE connectivity, built on BATMAN. Unfortunately, with the 2018.2 build of BATMAN, the OpenWRT configuration has changed, and most of the documentation follows the newer builds.
I am by no means an OpenWRT expert, but if I can, I am happy to attempt building a new firmware package that includes the newer kernel for the GL-iNet devices.