What an amazing thing you've done taking the time to share your knowledge for free with everyone - thank you!
This is very timely for me. I actually had just started paying a consultant to help me plan out a WISP, because it's so overwhelming starting out because you don't even know what questions to ask to get started (the internet is a great resource for so many things... but much less helpful when you don't have well-formed questions!). So far everything I'm seeing lines up with what I've researched myself or what my consultant has helped me with, so this seems to be an amazing free resource!
I even already learned something in the first couple sections - I had been using Google Earth Pro to scout potential tower locations, and I knew what a viewshed was, but I thought I was going to have to pay for ArcGIS or another program to generate them. For some reason I thought Google Earth Pro could only do elevation profiles! It's cool you mentioned using a drone; I was already thinking of doing that and it's awesome to know that's not a weird thing to do. Have you heard of drone photogrammetry[1] before? It's probably overkill but it seems like an interesting concept for generating high resolution viewsheds (i.e. taking foliage and other obstacles that won't show up on a topographic map into account).
My consultant helped me find a fiber backhaul solution; CenturyLink fiber dominates my area so I'm either going to be buying transit directly from them or buying transport to an internet exchange at the nearest metro area (the latter sounds way more fun to me and has some interesting peering options). But I'm still at the point of evaluating the customer base. So one thing that I'd like to see is more details on how to make first contact with potential customers to gauge their feelings towards a new ISP. So far I'm thinking of buying a list of mailing address from a mailing list broker, then mailing out postcards with a link to a Google Forms survey (and maybe an alternate option of just calling me if they don't currently have internet service). But I don't know how this is typically done.
I'd also like to see a section on skillsets that an ISP operator should develop. I started studying for the CCNA because I want to be able to wrap my head around the carrier-grade networking that will belie the business. It would be interesting to hear your opinion on how much you can punt on these kinds of skills vs. what you really need to know, or even when you should just hire the work out.
I also signed up to take a course on fiber optic outside plant planning because some day I'd like to level up to being a FTTH ISP. That's a whole different ballgame since you basically have to operate a construction company to plow/blow/splice all the fiber, deal with all the permitting, insane CAPEX etc. I know that's getting way ahead of myself and I should just focus on only WISP-related things to start but that's what I wish I could do if I were a millionaire. But if you have any experience with fiber ISPs I would be really interested in seeing that on your website as well (later!).
Another cool topic to cover (sorry if I missed it) would be the whole process of putting up an actual tower - I've heard that it can often be as cost-effective to erect your own rather than leasing (like pays for itself in 2-3 years). I was just reading a series of blog articles[2] a couple weeks ago by a guy who put up a ham radio tower that had lots of very interesting info and pics.
[1]: https://cloudrf.com/drone_photogrammetry
[2]: https://morsetutor.com/2014/09/tower-time-part-1/