The battery is indeed the HW part that has the most decay. But in that 5y time-frame the SW part is the one that is the most problematic. It would be nice to be able to replace the ROM easily after the EOL of the device. Will self-regulate itself immediately, as then incentives to have longer life is real and you cannot force customers to just buy another device because you decided it's time. By "replace ROM easily"…
The sad part is that you can't even do "ROM" replacements, it won't work for most people. Many countries have multiple apps that you more or less need to function in society, there needs to be a requirement for those apps to be installable on jail broken phones, not just via the official app store, if custom firmware is to make sense. Otherwise that old phone isn't going to provide much value anyway. 10 years of soft…
That will not happen.
You can't just allow banking and financial software to be run on a compromised OS. It is great for you but terrible for older people who would be exposed to rampant criminal fraud.
The better approach is to force OEMs to support their phones for longer. 10 years is realistic.