RE: Subtitles
I don't think branching really works well enough for what you describe. The crawl presents a unique opportunity to get in/get-out as far as the branching goes. And the crawl is- what? 30 seconds? What would be the total run time of all subtitled scenes in RotJ? Assuming you have to do it scene-by-scene instead of shot-by-shot (due to the non-seamlessness of branching) you'd be looking at a substantial runtime.
Are subtitles not any better on BD? I thought the increased resolution and raw computing power would allow for some nice anti-aliased/high res fonts for BD subs, but I don't think I've yet seen any subs on BD.