The "bare minimum for a non-disposable, consumer friendly, half environmentally responsible phone" starter pack.
Also the custom ROM ability should not be merely a bonus. IMO it needs to be legally mandatory even above standardised charging connectors. It costs effectively nothing to implement because the base OS and general architecture supports it by default, the manufacturer simply needs to not disable it, and it is by far the most important thing for keeping a device from becoming unusable and possibly even a cybersecurity risk with age. Also just in principle, I paid for the hardware I should be able to put my own software on it.