It works. Project completed.
Minimalist implementation of a Wemos D1 Mini shield for either a RFM69HW or a RFM69W module (both have the same pinout). Final build uses just the PCB, the RFM69HW module or the RFM69W module, two 8-pin headers, and a length of wire to serve as the antenna. This minimalist design both simplifies assembly and keeps the PCB cost low.