Every one I know have a super slim phone, then a case to prevent it to be broken and make the phone not slim anymore and then a second battery. So why not make a less slim phone with hardened chassis and a longer battery ? And market it as such (you want slim that last 8h and you can't plug your earphones, go Apple, you want solid that last 2 days and you can plug your earphones, buy Me)
And they also should embrace XDA community who work for free in advocating "a phone".
And they should also accept that a premium 4.5 /4.8 screen phone is also in demand, not just 5.5 and 6.0.
And give removable battery so we, paranoid, can really unplug the phone without having to put in the fridge.