I’m still determined. Looking for the ideal solution for Wi-Fi indoors, when you need to build smaller cell sizes than traditionally is the case.
20180910/DuckDuckGo single room low power wi-fi access point
Bingo! I found this really great article, in research paper format, from Cisco on engineering wireless networking for densely populated spaces like auditorium halls.
20180910/https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-1250-series/design_guide_c07-693245.html
Alas, many of the numbers on the space recommendations do indeed assume larger interior spaces. For example, some of the smallest coverage numbers are larger than some houses. Nevertheless, the directional antenna recommendations are useful when you only want to cover a small space.
So, I didn’t quite find what I was originally looking for, but I got pretty close. That’s simply because, as I noted, the “small” cell sizes still weren’t small enough.