With all due respect, I believe this CAN be done, but not with the simplicity and not as "live" as in Sketchup.
"Live, Sort-Of"
In the 3D OpenGL view, your "section line" would be a large block used to SEO the target object. You'd pull the block around and push it into the object where you wanted a peek. This could be quite slow depending on the complexity of the model.
"Animation, More-Or-Less"
I suspect that with a little GDL, this large block could be moved to SEO the model, being moved through the rebuilt-every-frame model with code linked to the animation frame like we do with the opening door trick.
Any GDL experts want to tackle this one with a short script for a parametric block with a displacement link??
Dwight Atkinson