- 1. Supply chain / component R&D -
You will be very, very hard pressed to source a pre-existing, high quality, non-exclusive 5.4" display with a hole punch. If you end up doing this as your own startup then you're going to start by trying to buy off the shelf parts to keep costs down. But that display you want is simply not on any of the development roadmaps for the major component manufacturers. The industry has its own momentum, and the component suppliers have also been looking at the trendlines so they are building bigger and bigger.
If you can't find the screen you want in a catalogue then you have to pay someone to build it. Convincing BOE et. al that your phone will sell enough to pay off R&D costs is unlikely, so be prepared to pay several million bucks in NRE to make it worth their time (it might still not be) and the wait a year for them to spin up the fabs. So ~$5M and 9-18 months later you have a display.
- 2. Big players are uninterested, not uninformed -
Big companies are drowning in market data. They know some people really, really want small phones. But it's a long-tail opportunity they're willfully ignoring, and people who need phones will still buy something even if reluctantly. I've been in the meetings, small phone advocacy goes nowhere.
Also I'm a little surprised you're hoping an online petition will work after your prior experience trying to influence your acquirers. I presume you saw the inside of Fitbit / Google and how decisions are made...
3. Android OEMs can't make a good small phone, even if there was the demand to produce it at scale
Because of how efficient Apple's SoCs are compared to Snapdragons, Android phones typically have much larger batteries than iPhones while getting about the same battery life. Big battery requires a big phone. The occasional somewhat small Android phone (for example Galaxy S10e) tends to have awful battery life.