Main one right now is a highly unsecure Redmagic that seems to have the highest amount of metal and glass for the exterior out of anything I've seen

If a manufacturer would make a phone with nothing but metal and glass for the exterior, I would upgrade to that

Another upgrade would be all safe materials inside the device

A side-grade from there would be the ability to ask the manufacturer's servers to unlock the bootloader

Another actual upgrade would be a bootloader the user actually controls