I know everyone here is tired of listening to me say this (
), but I think that Apple should just take the 12" PowerBook, upgrade it to match the MacBook Pro's specs, remove the optical drive, add in an ExpressCard slot, and fill the remaining space with more battery. Then, include a small, bus-powered Superdrive with it. For those times when you need an optical drive, you have a slim, convenient external. For the rest of the time, leave at your desk.
(Has anyone else noticed the built-in dictionary doesn't think Superdrive is spelled wrong?
)