From a WISP point to multipoint radio perspective, pure mesh is a really bad idea (due to half duplex medium and CSMA hell).

I admire the internet research work that APNIC does but it looks to me like they're re-inventing the wheel here, versus mature and stable, relatively low cost commercial 5 GHz band point to multipoint radio platforms like the Ubiquiti Rocket5AC gen2 and its associated CPEs, Cambium PMP450/PMP450i, ePMP series, and the various 802.11n and 802.11ac based Mikrotik solutions for point-to-multipoint 802.11 based last mile. Or Mimosa's 802.11ac based 4x4 MIMO platforms.

If you want to have a community WISP that operates with purely open source software, and are willing to forgo running an OS you can mess with on the radio itself, there's nothing stopping you from doing all of your network management and backend operational software on purely GPL, BSD and Apache licensed software.

There are significant performance advantages to using a 'mature' commercial WISP PTMP radio platform, one example of which would be:

1) ubnt rocket 5ac gen2 radios

2) RF elements 30, 60 and 90 degree horn antennas

3) ubnt powerbeam AC ISO gen2 CPE radios.

The PDF spec sheet for this apnic thing shows that it's running on a 7-year-old 802.11n based chipset, functionally equivalent to 802.11n cards I could buy for Mikrotik routerboards in the year 2011, best possible modulation is 64QAM 5/6, while the current generation of PTMP radios mentioned above are all capable of 256QAM (much better bps/Hz in a given TDMA channel size like 20 or 40 MHz) and are 802.11ac or 802.11ac wave2 based.

One of the problems with mesh is that you end up with antennas that have very, very spread out RF patterns, because every node needs to talk to multiple neighbors. It ends up crapping all over the 5 GHz noise floor in a given area, and eventually becomes a CSMA nightmare. Whereas if you have a system with focused, shielded sector antennas for AP sites (or horns), and directional parabolic dishes for client antennas, you can scale to a much greater degree.

Dedicated purpose WISP PTMP AP radios like the Mimosa also adapt 802.11ac chipsets to the unique timing, timeslicing and TDMA contention problems of having many individual clients, with different RSL levels and modulations, at varying distances located many kilometres away from an AP site. Using an off the shelf 802.11n chipset will have significant performance issues. All major PTMP AP radios nowadays have a built in GPS receiver for the AP radio, and 'slave' the CPE radios to them to coordinate timing. This greatly increased the aggregate throughput (in Mbps) and capacity of a single AP radio and sector antenna. This means that you cannot connect a generic 802.11n or 802.11ac client such as a laptop or tablet to a ubnt airmax or mimosa gps-synced radio system, and that's an intentional part of the design.

If you want a mesh for resiliency, a common topology is to connect various AP sites together for backhaul purposes by dedicated point-to-point links (again with tight RF pattern parabolic dishes, or something like the rf elements ultrahorn, or licensed band radios), put a router at each POP, and form a "mesh" at layer 3 with common OSPF and BGP network topologies in a private AS.