I was discussing this with a friend today and our feeling was that, for 20 bucks a figure, they had better include every conceivable accessory that the character had (removable helmets/switchable heads, multiple weapons, lightsabers AND lightsaber hilts, cloth robes/capes, and so forth) and that, for a character like R2-D2 or Yoda who are, as P-Siddy noted, much smaller than other characters, they should come with an even larger number of accessories.
The real ideal, I think, would be if they did a build-a-figure aspect of this and included the smaller characters in pieces. Namely, you do a wave 1 with Maul, Luke, Sandtrooper (ugh, why not a regular Stormtrooper?), and someone else, and have each include a piece of R2-D2. Ditto with wave 2: four figures, with extra parts to build a Yoda. Wave 3 could be someone like R5-D4 or a Jawa. That way, you're making each figure as important as the next, and offering something cool as a pack-in along with the higher price.
Just a thought.