Small, sturdy phone to fit in my back pocket
It is an indictment of capitalism that it is now impossible to find a small sturdy phone.
Manufacturers are competing for biggest and thinnest, but I ( and many others ) don't care how @#$%ing thin my phone is, I just want a smartphone - like my last smartphone - that does the job, has a recent OS, doesn't break and fits easily in my pocket.
3.5" is a perfectly adequate screen size. 0.5" is a decent thickness.
Now, make that phone !