I second Joel's enthusiasm! Just to throw another candidate into the mix, Opera also has "Opera Mini" which runs on Windows Mobile. (I can't keep track of all the Opera flavors. I suspect but am not quite sure that Opera Mini is the same codebase as the Wii browser, and that both are based on "Opera for devices".)
In some ways, the restricted nature of these devices is actually a virtue for users, and an opportunity for web developers. Users will nearly always have their phones with them, but phones are still little islands unto themselves. Applications that can run the same on (or are at least compatible with) a user's desktop as well as her phone or console provide a seamless experience that increases the value of the application. (Why worry about messy PDA/phone-to-PC sync if you just use the browser on the phone to access the same apps anyway?) If GWT can make the construction of such consistent user experiences easy to do, then I think we will have done a huge service for web users everywhere.
I think this is definitely worth pursuing, even if it does sound a little wacky. In support of the effort, I point out that Google has ported GMail and Maps to phones, indicating that there is clearly demand for this type of integration. Meanwhile, as I understand it, Internet access over such devices is quite common in many parts of the world, so there may also be additional hidden demand.
That said, I'm a little unclear on the specific use of deferred binding that you are proposing. Are you suggesting that we introduce "keyboardlessness" (for example) into the deferred binding mix, as a flag to enable globally? That would immediately double the number of generated permutations. Or are you suggesting that we just add targeted browsers individually, such as "Firefox, Opera, IE, keyboardless Opera, ..."?
Meanwhile, the EntryPoints are currently essentially statically processed. Are you proposing that we have the nocache.html dynamically compute entry points along with other stuff? That affects bootstrapping (though you're already working on that anyway.)
Can you throw out a little more detail of what you had in mind?
Finally -- just by way of reference, I posted about some of the capabilities of the Wii browser here:
http://groups.google.com/group/Google-Web-Toolkit/browse_thread/thread/6cf1f3237555f3c4/fd976fdeb8f64ab0?lnk=gst&q=wii&rnum=1#fd976fdeb8f64ab0
- Dan