The reason for a removeable battery isnt so much for the ability to carry an extra one around already charged, but is because they can ONLY be a charged a certain amount of times before they fail, have a much lower capacity or the controller chip thinks its been charged a set amount and refuses to charge any more even though the batteries themselves might still be fine.
With other phones you just buy a new one, change it, throw the old one away and carry on using your phone for a few more years. With a built in battery you end up throwing away a perfectly useable phone and buying a new one for hundreds of pounds rather than the 10 pounds or less for a new battery.
As for the stereo seperation issue on small phones surely the answer would be obvious? Have the speakers firing out of each end of the phone (top and bottom technically). This instantly gives a wider soundstage but with the added advantage of not taking up any front real estate,
So somebody could make a phone with a screen totally covering the front but that still has bigger areas inside the phone to develop a richer base by having the sound chambers behind the screen
This could mean an almost borderless front, larger sound chambers for better base response and better stereo seperation, maybe even kicking the ends at a slight angle to give a forwards preference with viewed in landscape mode.
it would admittedly make the phone slighly chunkier but if done with a curved rather than a flat back you wouldnt really notice the extra space that much plus it would make the phone more natural to hold
So a phone could be made effectively thin and flat but with a sound chamber clipping over rear facing speakers which then directs the sound left and right (landscape mode) without adding any extra space on the front or any extra weight.The main body of the phone could still be made watertight too as it wouldnt matter if liquid got into the sound stage area. The phone could even have the option of being used without the sound enhancer if necessary with the addition of normal grilles over the two rear facing speakers for people who dont need the stereo seperation for films and TV or music but whom just want "sound"
This design has always seemed so obvious that I am amazed nobody has tried it yet
Heck the extra rear cover (sound expansion shield) would even act as extra protection for the phone as it would be easily removeable and replaceable and could even give the option of other rear shields too like larger batteries or other add ons, This could be accomplished with point contact pads rather than a plug socket arrangement to make it easier to avoid moisture ingress.
It would certainly improve the stereo seperation, should give better base response and could potentially be a flexible way to add various functions to the phone like POE ethernet port and charging, extended WIFI, high capacity battery maybe even a slightly reduced sound port but with an added mini subwoofer to accentuate the sound even more into a minimalist 2.1 output and other things I wouldnt even think of. Perhaps even the ability to purchase hobby skins for electronics enthusiasts to build their own projects into them like a hand held mobile phone arduino type option for bespoke applications such as researchers or field engineers.Heck it could go full techie with giving companies the ability to create CCTV monitor shields so you can plug in CCTV cameras up a ladder to set them up, multimeter clip on and even an oscilloscope add on shield,
Or more mainstream add ons like an SSD shield and for DIY laser measurement or plum line laser attachments and pipe, wire and power sub surface scanners, ethernet diagnostic scanners and a variety of other things for various trades like thermal camera shields or 3d filming shields etc etc. The list is only as short as a persons imagination and market demand
A phone like that could be the BBC micro of the 21st century with very little change from the normal format and a bit of imagination
This was an idea I had after seeing my first touch screen almost a decade ago and assuming this type of product would appear "soon", but I am STILL waiting lol DOH
Its also about time someone made a bluetooth to landline plug in dongle so a mobile phone can work as your house phone when in vicinity giving you all of your contact details available regardless of whether youre using the house phone or your mobile line to make or recieve a call, I have been waiting for THAT product since bluetooth headsets first appeared as it seemed like the obvious next step.......also still waiting for THAT product too lol