Right, I believe the comic issue that storyline started in was called "Daughter of the Demon" and the BTAS episodes were The Demon's Quest.
I think that'd make a good story, but I don't think it would be a good intro to Robin. I think you have to show the murder of the Flying Graysons and how taking Dick in effects both Bruce and Dick. How it brings some much needed humanity to Batman, while at the same time how he could very well be scarring Dick Grayson for life by making him into Robin.
In my mind I see it as a trilogy telling Grayson's story arc. The murder, adoption and mentoring into the early stages of Robin in the first film. An established Robin in the second film building his and Bruce's relationship. The third film brings it back to the first with the full uncovering of the murderers of the Graysons, Robin being left out because Batman fears he will be consumed with anger and vengeance(Robin's Reckoning basically) and him splitting from Batman, abandoning the Robin persona and becoming Nightwing. Mix Robin's Reckoning from BTAS and Batman Year Three.
One could do the Demon's Quest storyline, but it wouldn't necessitate it being Dick Grayson that is nabbed by Ra's. It could be Jason Todd... which actually could be worked into making an adaptation of A Death In the Family since I'd rather see it be Ra's that the Joker is connected to rather than what was in the actual comic. I really like what they did with the Under The Red Hood DTV. That might work out better and get Jason travelling internationally in a more interesting way.
I like some of your ideas, i've been trying to propose for a long time that the Batman franchise could become like 007, having an infinite number of movies, with Batman Begins and The Dark Knight being treated as Batman's Year One, vaguelly mentioned, with Joker, Scarecrow and Two-Face being active but with the possibility of retcorning some things from these films like having Two-Face alive and the joker with his comic origin.
I would do a trilogy for Robin too, but it wouldn't be from Robin to Nightwing, it would be a trilogy for the evolution from Dick to Robin, in film 1 he's adopted and discovers Bruce is Batman, in film 2 he's being trained by Bruce and helps him in an Oracle style, place Lucius Fox has been filling, and in film 3 he finally becomes Robin.
I say, give time for the characters to develop, no need to toss Batgirl right after Robin, Batman movies can easily work with the Bond formula of a Bat villain each film, cars and cool gadgets, and maybe even a love interest for every movie, in fact, it can be deeper than Bond films while having a similar formula.
Batman is full of cool villain, i also proposed a tv show, something i think could work better for Batman