For people needing alternatives. I've had good luck with foritgate. Some of their APs are dogs, but the fortios in general has been decent.
I'd been wondering about this.. Ubiquiti's wan and firwalling is super weak, especially for multi-site, when compared to some of the sd-wan products out there. What's wrong with the ap's? Have you used the switches? How much of their kit can managed via a single console?
From what I understand their E and F series APs are solid, the ones before just had bad performance.
The switches have been pretty solid. Everything can be managed off the fortigate, I think they also have a cloud management platform.