It would probably be easier (and a lot smarter) to just make a psuedo-ChromeOS, something that boots a Nokia / Nokia-esque kernel and initrd and then just starts X and a web browser (maybe Chromium will start to build for ARM soon, or maybe Tear/some Firefox varient/pick your browser of the day), as opposed to trying to shoehorn all the Google cruft in.

ChromeOS's main unique "features," such as encrypted loopback user data storage and trusted boot are not very feasible on a tablet anyway (and I'd argue not very useful in general, but someone thought ChromeOS was smart...) . Trusted boot isn't even in the ChromeOS developer tree yet, since it'll require custom hardware and firmware - basically a lot of what ChromiumOS is right now is Ubuntu 9.10 with GNOME taken out, replaced by a little Clutter-based WM and login screen and an encrypted home directory.