[livueta]

Just as a note: you can easily configure AREDN to not use non-ISM channels.

Regarding custom firmware: yeah, but it's really openwrt with some CGI scripts. If you're not trying to specifically join their preexisting networks, you can accomplish everything it does off of vanilla openwrt with not much effort. I think understanding what's actually going on under the hood in networking terms is valuable enough to skip the preconfiguration, though I guess that depends on the exact deployment case. If this isn't intended to be used militarily in any way and is just putting up infra in rear areas, maybe that doesn't matter.

This post ended up a bit more negative than I intended, so I should say that I have successfully used AREDN (or similarly configured openwrt) on Ubiquiti APs with yagis to do more or less what the OP is asking for, and it works pretty well. This is overall a good suggestion.