How about this: create a keyboard base unit (MacBase?) that includes a pointing device (trackpad) plus the CPU/GPU/etc for running OSX. It would have one or two hinged mounting points. Alter the iPad just slightly to include one/two mounting sockets on the side (not standard iPod dock ports).
When the iPad is mounted on the keyboard unit, it uses the iPads display, battery, and flash storage to function as a full OSX computer (using the keyboard unit's CPU/GPU). The "lid"/iPad can be folded down on top of the keyboard unit via the hinge mechanism.
When the iPad is removed, it uses a second internal CPU/GPU to run iOS as a normal iPad. Note: the keyboard unit would be non-functional unless the iPad was attached.
Best of both worlds?
I think Lenovo is building or was planning to build a device like this. Problem is, the keyboard part runs Windows, but the detached tablet part has little or no programs built to run on it. Also, I don't think data syncs automatically between the tablet and keyboard parts. For instance, the tablet part runs some kind of calendar app that doesn't share the data with the calendar in Outlook on the keyboard part.
I think Apple is smart to build the iPad as a stand-alone device, wait a few years for the iPad apps to mature, then when they finally build a combo device, there will be plenty of apps for it in both modes. Oh, and what with the app store for OSX and Lion getting some iOS like features, by the time Apple comes out with a combo device, many apps will already be available with versions for both modes, with a smooth way to sync data between the keyboard version and tablet version, so you can play Angry Birds sitting at yur desk with the keyboard attached, then keep playing from the same level on the go with just the tablet part. Apple shouldn't, and I'm thinking they wouldn't, build a combo device until the software and apps are ready to do this.