Recently I learned, and was intrigued, by two products from WaveShare, both enabling a small footprint Raspberry Pi Zero (2W in my case) to fill a Raspberry Pi 3 case by including a suite of adapters, plugs, and sockets. With the uninspiring brand name, "Raspberry Pi Zero  to 3B Adapter."
The "A" Board
The "B" Board
Wifi on a pi3 with NetBSD?
- RPI3 and RPI0W builtin WiFi - bwfm(4)
- "Note that the built-in WiFi in the RPI3 is not yet supported."