So Graphene is actually not limited to the developed/western world. As for not supporting other devices, I believe the reason could be the team size and the fact that the fragmented Android world is known for unique shenanigans of every OEM. Besides Google's update/upgrade cycle is another reason it is an appropriate choice.
You can have the best alarm system in the word, if you leave the back door open and anyone can just walk in from the street.
So just give me that alarm system for my tent, please. It will do fine for my case.
Our requirements are not at all exotic or outlandish, the fact that most OEMs don't meet them says more about how far behind most OEMs are, rather than our standards being unrealistic. We've also been told that they're not unrealistic in practice from numerous OEMs who want to build a device that meets our requirements.
It is also important to note for Pixels specifically that since the 8th gen Pixels, they receive 7 years of support. Additionally, they partner with iFixIt to provide official replacement parts for the duration of the device's life. I'd say that's pretty sustainable, especially when you consider that the Fairphone doesn't actually provide proper support for the amount of years they claim, since they have consistent delays in providing patches.
As for the requirements, I will take your word for it. And I do appreciate that you put the emphasis on security as it is often overlooked. I guess what I'm saying is that having control over my phone (as opposed to BigTech or apps having the control) is for me a much higher priority goal than just security by itself. Hardware reparability is (again, for me) a close second.
Anyway, I hope you find a good partner for the phones, and I'm curious to see what you come up with!
Is this really that big of an issue? It's like a couple dollar fee every 4-5 years or so.