Thanks for starting this @elorimer.
I am afraid that I know ‘not a lot’ of the scripting languages, or how to access OpenWrt using them, so will watch this thread with interest.
I do know Node-RED and have used REST API’s for that and other things. FYI Router I have is GL-X750V2 (Spitz)
I have a Node-RED flow that is able to access WAN signal strength and the available WiFi networks available, so I might be able to develop that further, but then I would need to be able to store the historic data. This is ‘doable’ as I have an RPI running on the Network already (PiHole).
I have installed VnStat and am running it to see what data is available.