Why not?
111 x 73 x 8.5 mm dimensions.

Add in a thin hardware keyboard that "clicks" on one side of the device's backside. It stays firmly hooked, is static (non-slider/non-adjustable).The keyboard measuring the same length, but smaller width and a thin profile. Something like 111 x 63 x 4.5 mm

When not in use, the keyboard can be turned the other way so that it clips with the keyboard facing "in" to be a single unit with your phone. That brings the total dimensions of the phone with the keyboard closed to 111 x 73 (slightly larger than SGS3) x 13mm (about as thin as the Droid 3).

Maybe not those exact dimensions/figures... but you get the idea.