I'm going to start this by saying I hope you're right about them introducing later elements sooner, but the manga and original anime series both had a crowd witnessing them fighting, and throughout the series both are shown to not care about being seen in their alternate forms, just their transformations. Ranma also never directly refers his girl side as his sister; in the first Kodachi arc, Girl-type Ranma (or Ran-chan) just uses his real name and people infer different things--Kodachi herself obviously doesn't think GT Ranma is Ranma's sister or she wouldn't be so insanely jealous of her still, and Tatewaki Kuno (Kodachi's brother) is just glad to know the pig-tailed tree-bourne kettle girl's name. Some of Ranma's classmates ask if GT Ranma is his sister, but he doesn't confirm it. Ranma used two named aliases throughout the series that I can --Yoiko Hibiki, Ryoga's "little sister," and Ranko, Akane's "cousin." The former was used just to screw with Ryoga, while the latter was used to hide from/interact with his mother, who would force Ranma to commit seppuku if she ever discovered he wasn't manly enough by her standards. It's this latter alias that I hope arrives sooner, along with Ranma's mother, who didn't arrive in manga until chapter 225 and only appeared in the anime in the last two episodes. It would be interesting to see Nodoka show up early and witness all the battles that "Ranko" fights (mild spoilers, but seeing what Ranko can do and how "she" acts is important to the relationship between Ranma and his mother), as well as to have Tatewaki and Kodachi to be fighting for and against Ranko instead of a second Ranma Saotome. The obliviousness of pretty much everybody to Ranma's curse, no matter how careless he was in hiding his secret, was an early running gag that ran out of steam pretty quickly for me.

I'm baffled that they didn't address the biggest plothole--why didn't they search for a cure before coming back to Japan?