"Also, how will they be able to tell if you are going international or domestic at screening and what you should or should not have?"
You show your boarding pass at the checkpoint AND at the gate. Both are potential gotcha points. Plus the reason many people insist on carry-on luggage is because they don't trust stuff to stay in the hold, and there's no way to ensure their security without risking another Lockerbie, so it's a no-win situation.