Despite claiming to be in love with him Shampoo seems to know nothing about him. Twice she has mentioned his chauvinistic attitude about fighting woman. She herself has seen proof that that is not true. Her whole situation started by him defeating her with a kick, he wanted to hit Kodachi during the rhythmic gymnastics match; he hit Konatsu when he thought he was a she, etc. He will and has fought girls in his male form (Herb before knew was male, Kiima, Rouge, etc.).
Ryoga’s curse will make him immune to Mordred’s spell.
Anyone who has watched the movie knows that Tetsuo is weak against energy attacks.
The Hiryu Shoten Ha is a completely defensive technique something that while Ryoga is skilled in isn’t his biggest strength. Not once during the entire series has Ryoga ever tried to use it in battle.
In an effort to sup up Ryoga Lathis has repeatedly given Ryoga knowledge that is detrimental to his skill set. Like joint manipulation and Pentakian Reverse Leverage Thorax. The use of the first ended in disaster while the second was used on someone way below his skill set. It’s the same reason Ranma doesn’t use the Yamasenken style or the Bakusai Tenketsu even though he picks up things at an insane pace. They just are not suited for Ranma's fighting style. There’s a reason he and Ranma have only fought once.
Lathis tried to make his fic as close to cannon as possible. Akane and Ryoga repeatedly like to rework scenerio’s in their head so it ends up Ranma’s fault some how. During TALB Akane glared at Ranma for making fun of Ryouga for getting lost conveniently forgetting that when she learned about the neko ken her first response was to see how many cats she could get on him. In fact any time Akane finds out something horrific about Ranma’s childhood she either beats him up because it embarrasses her or uses it to control him.
Nabiki is just as arrogant in fact more so them Ranma. She is opportunistic and thinks only of her immediate gain. She does not factor in the possible consequences of her actions. This is shown on multiple occasions such as her taking pictures of Ranma when she knew nothing about how Ranma might retaliate when he found out, not taking into account how dangerous it is to be Ranma's fiancée (which nearly got her killed, heck she herself thought she pushed Ranma to far), or what would happen to her or her family if she lost the 10 yen battle. The only reason she hasn’t been killed is that those Godlike martial artists have both a certain honor code and incredible self control and luckily the ones that don’t are weaker then the one’s that do. Nabiki jumped in to super villainy with this same mentality.
Ranma was perfectly aware of what could happen if he went cat as a boy in the presence of Nya-nya.