Yes, batteries should be replaceable and all those things you mention - '... the additional layer of plastic needed under the battery compartment ...', '... rep

Yes, batteries should be replaceable and all those things you mention - '... the additional layer of plastic needed under the battery compartment ...', '... replaceable ones are much more robust in design and shielding -- additional plastic ...' don't make any sense at all. Any 'need for any additional plastic' in devices with replaceable batteries is easily offset with the messy sticky tape Apple deems necessary to hold their batteries in place. In practice the battery usually just lies atop the circuit board with a thin sheet of some insulating material in between. That sheet of material is part of the device and does not need to be replaced when the battery is swapped, this in contrast to the double-sided tape Apple uses which needs to be replaced whenever the battery is removed. Replaceable batteries are no more robust than non-replaceable ones, both consist of a Li-polymer pouch with a bit of circuitry attached somewhere, the combination wrapped in heavy tape or shrink foil. Batteries should be replaceable without the need for special tools (a simple standard screwdriver (Torx or Phillips) is OK, pentalobe screwdrivers are not) OR they should last the life of the device without significant degradation.