Well, as one who has been watching this topic, I believe everyone just exhausted themselves.
But, the way you presented it does sound plausible. Though. I did notice something. If it wasn't Ranma, wouldn't most Amazons just generally not care about Genma, even if he was the father of such a powerful individual. Well, color me prejudiced, but I do believe if Genma would just abuse his 'authority' as the 'father-in-law' until the Amazons get so ticked off, they wouldn't even care if Ranma was to be Shampoo's husband, and chase both out. That, or as you say, Genma runs out with Ranma forcefully (or not) in tow.