Is it possible to make Modbook-style tablets from MacBook Pros ...?
You may want to look at this neowin.net forum post. A poster provides a detailed guide to converting an older plastic macbook into a working tablet.

Unfortunately, applying his approach to a newer unibody MacBook or MacBook Pro would be difficult since much of the structural rigidity of those notebooks lies in the keyboard plate. Cutting away that metal to fit your touch screen or pen tablet would leave only the relatively flimsy outer shell to support the notebook. Axiotron addressed this problem in their proposed (and now probably dead) Modbook Pro by building their own housing for the MacBook internals.