@alcinnz FWIW, my hesitation is largely that there are existing feature-phone offerings that address much of what I'd want, and waiting for something else which ... might well not appear or meet needs ... doesn't seem particularly rewarding for me.
I've been looking into this space for much of the past year, intensely for a few months. My view is that working with existing hardware would probably be more rewarding, and would be the fastest way to deliver a useful feature set. There are already several vendors who do this, Sunbeam (https://sunbeamwireless.com/) and https://dumbwireless.com/products/dumphone-2>).
There are also other options --- I'm looking at Sonim's rugged devices (they carry a range), and would be strongly partial to an e-ink hard-keyboard (T-9) flip device (there are several options close to this, none quite works for me).
We've already talked about what you want to do, and I won't relitigate that. But from a potential purchaser, this is my thought process and preference.
The other option I'd strongly consider would be a WiFi-only SIP device. WiFi is sufficiently ubiquitous that being able to move from coverage-zone to coverage zone would work pretty well. Much of the tracking of mobile comms is avoided (if necessary I could use a mobile hotspot). VOIP generally affords vastly superior call management / call filtering capabilities. From what I've seen of the space, this particular niche is poorly filled, whilst at the same time general frustration with direct-dial phone networks and mobile/smartphone tracking and distractions are an increasingly major turn-off.