Maybe even a
sorted list of all gateways in /proc would be nice to be able to
set up some more advanced (fall-back) scenarios with other
measuring methods/tools. And on the other hand we'd have the
possibility of batman-adv not interfering too much with the other
layers, instead tools explicitly designed for layer 2, 3, ...
have an interface to fetch the gateway information then which only
batman-adv knew before.

That would be even better than what I was suggesting. It would, among other things, make it easy (with the addition of some sort of directory in userspace, or redefining the gateway flags) to find the closest node(s) with some particular service. I'm thinking of things like "all squids that are nearby".

donald