Serves Samsung right for sealing the battery in. Much cheaper to send battery packs out.
If the replacement units are also experiencing problems, it may not just be a battery issue, but something to do with the design of the phone as well, in which case a removable battery wouldn't do anything.
It's entirely possible that it is just an issue with the battery itself, but it seems odd that the replacements would also have an issue. One would think that Samsung would have been exceptionally careful about identifying the problem and ensuring that it was fixed.