Goes against all Jobsian principles of simplicity, but damn it would be sweet.
Speaking from experience, and as a professional writer, I can tell you that I've been jonesing for an external keyboard ever since I got the Touch, and now with the notes widget onboard, even more so.
Years ago, back in the dark ages of Handspring, I had a visio with a folding targus keyboard and a mobile phone module. It all fit in two jacket pockets. So if I was going to interview a client or even thought I might possibly end up somewhere that I needed to write something of length, and yet didn't want to walk in carrying a laptop case because of whatever reason (it happens), then I could always be prepared to assemble my own mobile writing station on demand.
Now, here's the real <A HREF="http://bp0.blogger.com/_HuoQ6cddTD8/R5QEvoXgvfI/AAAAAAAAAkc/J8v1QbiqakU/s1600-h/iDream.jpg"> dream.</A> The Touch hooked up to a MyVu personal widescreen theater glasses AND an external keyboard. Movies, music, writing, all on demand, wherever, whenever. Nirvana. But, of course, Jobs would pull what's left of his hair out at such bastardization of the design principles. Oy.