There are several bugs raised relating to re-usable modules, in particular https://bugs.launchpad.net/kicad/+bug/1525095 and https://bugs.launchpad.net/kicad/+bug/1521062, the idea at least got some positive response, but without any commitment to implementation. There is not a directly corresponding item on the v5, v6 or CERN roadmaps that I can find.
I think it would be a substantial chunk of work to implement, there are quite a lot of complexities. I guess people will also want to include tracks, vias, zones, NPTH holes in their modules as well. What happens if you put a 2 layer module onto a 6 layer board (or other permutation)? Footprints have an FPID which may be in a local gp-lib-table, does the module need to have its own fp-lib-table?
There is probably something simpler that could be implemented more quickly, identifying the minimum subset that would be useful would be a good idea. I wonder how far a prototype could be implemented using a script.
There is a blueprint doc here https://blueprints.launchpad.net/kicad/+spec/layouts-as-footprint.
Hmm, the forum software reminds me I made almost the same post before. Well, that was over a year ago and I forgot. Considering the size of the task and number of wishlist items (more arrive every week), I think unless someone like CERN commit a bunch of resources to it, it will not happen for several years.