1. Define "separate." If one creates a node module that creates content types, then one must manage the extra fields - generally in new (i.e. separated from node & node_revisions) tables created by the module.
2. If one is talking about content created by other (e.g. core) modules, then the answer is maybe. Take a look at the sql rewriting hooks or whatever D7 has done to them.
3. Lastly, why? I would think that the overhead of managing multiple tables would outweigh any potential gains. I can't even begin to think what you would have to do to Views to make it work in your scenario.
    

Nancy

Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.