On the Hoth battle and energy shield, I always presumed that the shield was like the Gungans' huge shields - impenetrable by lasers etc, but slow-moving objects could move through without trouble. The only difference is that in ESB the shield is invisible - which is actually in keeping with all of the other energy shields in the OT, which are never seen. I really don't see what all the fuss is about.
On the notion of dropships, Adywan is right on the slow reveal to build up to the ATATs. However, would it not be possible to do a long shot of the Star Destroyer group as several dropships are launched (which would be tiny dots, really), and those dots arc towards the planet. It could be done in such a way that prolongs the "they're coming!" tension even further. Honestly, I'm just a sucker for all the space battle stuff, though, so the more of that fit in in any way will always get my vote!