You'd get a design identity ++ if the dovetail backplate was more similar to ejecting toast. . . .but looks like that isn't in the final anyway.
Did you consider radar[0] instead of PIR with the MPS430?
The main consideration for the motion sensor is power consumption -- Photon's PIR consumes ~2µA. Any idea what the power consumption is for these radar sensors?
The video I linked was from 7 years ago? Here is a more recent one but it doesn’t seem like he measured energy consumption: https://youtu.be/s-GzUTyIH9c
As validation of your PIR-Cam idea, LilyGo sells a PIR-Cam-SSD1306 combo board: https://www.lilygo.cc/products/t-camera-s3