[jws]

…and a flying pony.

You want a 40% space reduction and room for more batteries in exchange for losing an optical drive that accounts for 10% of the original volume.[1]

[1] The MacBook Pro has a volume of 2175cc. An internal optical drive is about 200cc.

[kylec]

Overall volume perhaps, but the optical drive takes up a lot more than 10% of the internal volume.