Well, the README does not tell about make full, whereas the images generated by make all do not appear to be used (at least the xen.xml template references the “full” version). Maybe this README would benefit from a bit more info ?
Also, building such packages separately, although it avoids full rebuild of everything, requires to install specific qubes devel packages, which ideally are only installed in a chroot to make sure they don’t pollute - or in a separate VM, but having separate temporary VMs to build each such package separately is starting to be heavy.
Maybe I’ll end up resuming my experiments with ISAR first 
… sooo many nested projects and soo little time 