I see the batman module is loaded. Does the 802.11s mode utilize batman? Under the 80s.11s mode, can I have multiple internet uplink nodes within a single mesh?
Our 802.11s implementation uses the HWMP routing algorithm in Linux by default with mesh11sd for management. You’re open to using BATMAN, but your mileage my vary.
In theory I don’t think there is anything stopping you from having two backhauls, just configure those devices as mesh gates.
Sounds like you are not a fan of BATMAN. My implementation is for a rural fire department. They have very bad cellular coverage in parts of the County. I purchased 5 units to use as a test bed. The customer is wanting to run ATAK on tablets in each fire truck for mapping and situational awareness. There will not be an atac server so all tablets will run in the peer to peer mode. They will all need to have static IP address assignements as there is no DHCP available. The ATAC units will automatically form a peer to peer if all units can see each other on the same subnet. I am not an ip expert by any means, so any insite would be helpful.
I wouldn’t say we’re “not a fan” of BATMAN, we just haven’t exercised it in anger like we have HWMP/mesh11sd, and personally I’m not that experienced with it 
.
We actually do use BATMAN for IBSS/Adhoc mode, rather than 802.11s. That might give you some hints in to how to configure it. We also use it in a fairly standard way as far as OpenWrt configuration goes, so you should be able to follow Testing to determine if you are a bot! which might help you.