The keyboard problem is a non-issue. On the go, you use the screen. When you place it in its nice shiny iPhone-esque dock at home, the screen is upright and a wireless keyboard and mouse can be used and it looks and feels like a PC.
In a mobile scenario you could have something like an empty laptop shell as a case. No display, no guts. The tablet docks into the top half and the bottom half is a keyboard. Probably wouldn't be any larger than today's MacBook.
