Yes, should be doable. I've been programming Sketchup a bit recently. Using Ruby (which turned out to be easy to learn) it is straightforward to generate useful object directly from code. I've put together most of a CupCake using Sketchup in order to learn from the design and make my own modifications.
Similarly, it should be straightforward to slice using Sketchup and Ruby. Basically, you use a section plane at different Z positions, let Sketchup create a group of the cross section and then process each slice. Probably the best idea is to figure out how to interface with a tool like Skeinforge to do the actual filling and generation of G codes.
Ideally, you'd be able to print directly from Sketchup and see the object grow as the section plane is raised. Sketchup has a problem with very small objects, as it was apparently more ment for building-size drawings. A work-around is drawing at a 10 or 100 times larger scale. Another issue is that it's easy to end up with "extra" geometry that's a PITA to clean up. With groups from section cuts curves get exploded to lines. This can again be worked around, but the general point is that Sketchup is not really a CAD program, unfortunately.
-Geert