OK so IPs from MAC addresses is pretty good but not a perfect solution.
This comment is interesting...
However, as Marek already wrote, the focus of the batman development moves to layer 2 where IP addresses are not used. On top of batman-adv, you can use any IP address distribution scheme you like. For example, you could simply run a DHCP server.
Batman-adv does indeed seem like the way forward. So, on top of batman-adv, what solutions are there for IP address distribution? What might you try in a situation where there is no obvious central coordinator to put a DHCP server on?