Well, me too, and that is exactly how I use my Pro1. Not with Ubuntu, though.
My point is that, for a phone to work as a miniature "laptop", all the functionality must be there in principle without carrying external devices along. For that is what a laptop is: a standalone all-in-one machine that has all required peripherals built-in. That you can extend functionality by plugging even more stuff into the device is a bonus, not a requirement.
This does however not seem to be what the OP have in mind: they seem to refer to the so-called "convergence" mode of operation, where the phone