As you say: "If there is any stray charge outside of a certain conductor, couldn't there be some on an internal surface of a huge, hollow conductor?"
Certainly! I think your confusion arises from a misunderstanding of what "outside" means in this context. Outside does not mean "the furthest surface from the center of mass of an object." It means "the surface of an object." Likewise, the "inside" of a conductor refers to the actual matter of the conductor itself (the atoms making up the metal, that is), not to any hollow cavity in the middle of a larger conductor.
Suppose we have a spherical copper shell - that is, a sphere made of copper with a cavity in the middle. If we put a positive charge in the middle of this hollow cavity, then the inner surface of the shell will tend to become negatively charged (as the positive charge in the center will pull electrons to the inner surface) and the outer surface will become positively charged (in the absence of electrons). This is essentially the situation you have described, and it is completely accurate.
Your instinct about conservation of energy is also correct. The reason that moving charges cannot be sustained in a conductor is because no current in a conductor is indefinitely sustainable without some addition of energy. So eventually the charges in a conductor must move to some electrostatic position.
I'm not sure if this answers your question completely, because I'm not quite certain how the two aspects of your question ("what is the mechanism by which electrons are propelled" and "why do charges end up on the outside") fit together, so let me know if you need any clarification.
Best Answer
The hollow neutral conducting sphere will experience an induced charge separation if there is a point charge in the cavity. If the charge is negative, then
So the inside surface will be positively charged and the outside surface negatively. And since electrostatic force decreases with distance, the inside is pulled in more strongly than the outside is pushed away. So yes, the charge in the cavity is trying to compress the sphere.
If it is earthed makes not difference. Then the outside charge is just able to move away from the sphere, and the inside will be able to acquire even more positive charge.