- 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...
Look at how long all of the requirement lists posted around these threads are. Some people really want a nice camera, some a headphone jack, some a SD card or big battery etc. I would expect that it's a fact of life in a small phone that you can't fit everything anyone might want, but everyone has a different list of must-haves, making it much harder to make one device that all of the small-phone-wanter market will actually buy.
And price. If you really want some one-off thing, you've gotta pay more for it. Would you pay $2k, $3k, more for a great small phone? Seems likely that such prices would help a lot at getting them made. But in reality, people seem to refuse to pay more than a modest markup over the mainstream model with tens of millions produced. Sorry folks, I don't think it works like that.
Worse, they expect it to be cheaper since "it has less screen and battery it must be cheaper to make!"