iPhone size is already too big (imho!). So Sony one is anything but that. Asus ZFs? Nope, anything but mainstream. These never released in many geographies including my country - the most populous on the planet and no it was not even too costly for here - and yes, they already have a sales/distributor channel/base here so they didn't have to setup anything.

There really isn't anything mainstream out there at all. Why? Majority, clear majority, of people rejected smaller size phones sadly.