Whatever you'd gain in thinness would be more than made up for by inconvenience of having a proprietary built in inflexible system. The bp isn't all that thick now. Flexibility beats a reduction in thickness imho. Smaller isn't necessarily better; and what happens when the built in proprietary battery dies? Send it back for a costly fix? No thanks. The nice thing about these units as they are now is that its really easy to swap batteries, and we already have the ability to use nimh if we so choose. Mary mary