Compared to your ideal specifications, my wishes are: support for microSD card storage; battery that easily and reliably lasts a full day with moderate phone usage; fingerprint sensor, not necessarily on the power button; camera decent, not necessarily great (I don't care that much about low light performance, for example).
I'm tempted to sign up even with the specifications as you list them though. Missing microSD card support could be the major dealbreaker. Or alternatively some other user-friendly reliable method of getting lots of files from my PC to the phone's storage, but so far I haven't found any. Early Android versions supporter USB mass storage and that worked pretty well, but the transfer method implemented on newer versions is very slow and never works reliably for me.
Those additional requirements further splinter the market.
But what's the point in buying a small phone if it does not meet these standards, which are all about longevity? Then it will just be unusable in ~2 years. Which would make it no better than the otherwise perfect small phone I already have at home, the Veer.