How do you feel about "A" being already occupied by "Apply" System-Settings-wide?
And, I hate to say it, but both "&B" and "&L" are in use already for the profile page (for "Change key&board brightness:" and "When laptop &lid closed:", respectively) so those would require changing. Which of course is a nightmare, there are barely any useful letters available, I struggled to find a mnemonics scheme that makes sense at all.
I would not be opposed to a patch that removes most of the mnemonics and lets the system automatically assign them, if it's even up to the job. The way it is right now, mnemonics in the Power Management KCM are essentially unmaintainable and untranslatable. (Or are we actually expecting our translators to avoid conflicts between labels?)