Super Carrier buckling spring 122-key (membrane is fine but capacitive preferred for reliability), with a volume knob, trackpad to the right of the numpad, trackball in the M5-2 position, trackball in the M5-1 position, trackpoint and buttons in their usual spots, and natively PS/2 in interface for the keyboard while USB for the pointing devices, but with each operating as in independent device (so basically an integrated USB hub for them to share, plus one or two ports available outside the case), in black with chrome highlights, original silver/black metal IBM logo, dark blue backlighting but dim with dark red backlighting (again dim) around the lock keys when locks activated.
And a ridge at the top to act as a pen holder, somewhat more defined than what's on the existing cases.
And software to easily map the extra keys to anything you want, including keyboard-side macros saved to memory in the keyboard itself.
And a dedicated calculator function for the numpad.
And an ESC key, with either a Cherry blue or white ALPS switch just for fun, in the upper left of the keyboard, with a doubleshot Geekhack key attached.