To give the Ewoks their due.

George seems to have always intended a stone-age culture to take on the space-age Empire in a final act in a film (always difficult to tell with George).

If the Ewoks are transformed into tougher alien people, having them take the Imperial legion by surprise is an important rogue element that the Emperor hasn't anticipated.

I'd still augment that with footage of Rebels with guns taking on a larger Imperial presence, the ship would be large enough to carry a significant task force and equipment.

In the current versions the Rebels (outside the big six) seem to vanish after leaving the ship.