As to the Choose your own adventure book series (which yes I was a fan of) that doesn't really count. The author for the most part had those planned out before you read them and even then they have a set ending. The Anime Adventure and the like is a good example and there are a lot of good stories there but almost all of them lack one thing...an ending. A good story has a beginning a middle and finally an ending. I've yet to see a good AA story or any similar site that was written that had that sort of structure. Not that I don't like lots of stuff that comes from there but some of the stuff that entertained me on there wouldn't be enjoyable if I was reading it as one coherent narrative rather then a branch of choices. You have to hold it to a different standard and that's usually due to the author/authors having zero vision on the next paragraph much less the ending.
In regards to the curses even by your argument that they are activated when it's funny let us keep In mind that first and foremost Ranma is a comedy series. Thus funny moments should occur. Second Ranma switches forms willingly at least once a day when showering (which can lead to humor and often does but keep in mind he rinses in cold water seemingly regardless) so that's simply another opportunity. Third Nabiki requires photos of Ranma to sell so she would I'm sure arrange for him to end up in his cursed form if enough time passed. Fourth the most common method that we've witnessed in regards to awakening Ranma is Akane hitting him with water or his father tossing him out of the window on occasion. And even if you want to haven him wake up not using one of these methods he spars with his father outdoors almostvevery morning. They seem to make a game of getting one or another wet on occassion so that is yet another opportunity. Fifth the guys at Furinkan all know about his curse and are all perverts I have no doubt they subject him to some unwanted changes at least a few times in an average week. Sixth as Spok said Japan is an island nation in the Pacific rain happens their sporadically, quickly, and unexpectedly getting caught without an umbrella is likely very common. Seventh Ranma on occasion invokes his cursed form willingly in order to get food/scam someone/spy on someone/work/etc. All of those to me indicate plenty of instances where Ranma could very plausibly be in his cursed form at any one time and preclude an author who is writing about this series for a significant chunk of time from not mentioning him in his cursed form if only in passing.
Like I said you don't need gratuitous Ranma-chan (you are correct I do like It however) but if you end up rarely if ever him changing into it with no explanation of a method he is using to avoid the change it feels like you're simply being sloppy. If you don't want to focus on his female form that's fine I've read plenty that don't have him in it but come on the curse I've summarized above should get activated at least once or twice a day so it should at least be an innconvience to him and not something one can ignore.