Hi,
I'm not so deep involved in batman routing to find a solution. I hope you can find a way. But for now it is not so important. But if one node announces a HNA and a different node that just has fun to "turn off" this node can simply send the same HNA. If you say the first HNA is the right one, then what happens when this node gets the forced disconnection after 24 hours by its internet provider?
I think it is difficult to find a solution for this. The best is to keep all nodes active but kill the HNA if not reachable?
/Stephan