Well, I was thinking that it would either be something so extreme that Principal Kuno is taken out for an extended period of time... perhaps a coma? Later on, when he comes out and sees all the ridiculous shit that's gone on in his absence, Zeke obtains Special Friend status and PK becomes an on-again/off-again menace.
As for how? Easy. Lum gives Tatewaki Kuno some alien explosive device to use on Zeke - one that has the explosive capability to level the school in the manner you mentioned. Lum knows that Zeke's wily enough to escape any permanent harm, but whether or not he is defeated by it is questionable. The lead-up for that is that, due to his fame, Zeke is already regarded as awesome opponent material by the fighters at Furinkan. Ranma will initially challenge, but once Zeke says he doesn't want to fight, then that's that - Ranma's scruples keep him from fighting an unwilling opponent for sport. Ryouga, on the other hand... he got pissed off that Zeke refused his challenge. Turns out that Ryouga issued a formal challenge some time ago, but due to his eternally lost boy syndrome he never received Zeke's equally formal reply stating that he declined. Of course, Ryouga blows it all out of proportion and charges Zeke... who uses Ryouga hot-headed state against him with a simple aikido throw and a 'boost' of wind to hurry him along... through several walls. Tatewaki is impressed, but before he challenges, Lum shows up, scares the bejeezus out of him (ONI! AAAUUUGH!), and she offers him the bomb which he accepts, because Kuno is just unprincipled like that. Zeke recognizes the weapon, tells everyone to run like their lives depended on it (because they did)... but not PK. He thinks he can disarm the damn thing. Instead, he just cooks the damn thing off and lands himself in the hospital for an extended stay.
Bonus: Zeke finds out about what Lum did and knows that giving an Earthman such a weapon is a huge no-no. This bit of blackmail material in hand, he threatens Lum with the prospect of telling her dad. the only reason he doesn't (and thus rid himself of her entirely) is because he's been studying crime and punishment among the Oni... and suffice to say, it isn't pretty.
The NWC will attend at Juban, just long enough for Furinkan to get back up on it's feet (the school board isn't taking any chances in whether or not PK wakes up anytime soon)... but it's still long enough for something to happen. (I'm thinking of having one of the Senshi use that line that I see in someone's sig floating around here: "Did you do something rash?" "Yes, and it was GLORIOUS!") Later, when Soun and Genma receive the formal request to have Ranma and Akane transferred to the special wing at Mahora, they agree to go with it because they know that A) Zeke is there, B) weird shit happens around Zeke, C) It's a special training school - one perfect for the Anything Goes school.
To avoid total curbstompage, not everyone will be around at all given times. Sousuke and the MITHRIL elements will have missions to run. Ranma will have new cures for his curse to hunt down. Zeke goes on walkabouts. Negi makes trips into the Magical Realm with his students. Miyuki takes on a few missions here and there. Kodachi occasionally has Yakuza business that takes her out of town (she has to fill in for her father while he's out cold). Matsuri's needed for a mission at the SSA. And the Government is perfectly accepting of all this - the entire point of the school is simply to keep better track of these people and make sure they don't do too much property damage. Also, there will be Big Bads in combinations as well by this time.
As for Yomiko Readman, her domain is going to be the satellite library that is part of the Special Youngsters Wing... of course, she'll still make trips down there with the Library Expedition Team (hell, she'll probably become their Faculty Adviser). To her, the traps would just be training to help her keep her edge. Also, once she sees that the water is having some sort of preservation effect on the books she'll relax considerably. Reference here: http://www.mangafox.com/m...a/v02/c009/12.html It's preservation - books do not soak for fifty years and come out undamaged. Hell, even sitting on the shelf for fifty years it doesn't do them any favors.
As for the Cardian battle, I'll go for it. In fact, I've thought of a decent intermediate weapon for Zeke - they happen to give him a full survival kit for pilots that have to ditch their aircraft... minus the pistol. This means he's got a decent survival knife on him. A knife he can charge with his spirit energy and use to good effect on a Cardian. It won't be Usagi's attack by a long-shot, but it'll be better than the weak infrared lasers from the VR Arcade. I can see him taking down one or two Cardians this way with Lum's help, but once he sees what he's really up against... yeah.
And yes, Zeke is most definitely the result of a butterfly that decided (not) to flap it's wings at a particular moment. Chaos will be most displeased.
As for how? Easy. Lum gives Tatewaki Kuno some alien explosive device to use on Zeke - one that has the explosive capability to level the school in the manner you mentioned. Lum knows that Zeke's wily enough to escape any permanent harm, but whether or not he is defeated by it is questionable. The lead-up for that is that, due to his fame, Zeke is already regarded as awesome opponent material by the fighters at Furinkan. Ranma will initially challenge, but once Zeke says he doesn't want to fight, then that's that - Ranma's scruples keep him from fighting an unwilling opponent for sport. Ryouga, on the other hand... he got pissed off that Zeke refused his challenge. Turns out that Ryouga issued a formal challenge some time ago, but due to his eternally lost boy syndrome he never received Zeke's equally formal reply stating that he declined. Of course, Ryouga blows it all out of proportion and charges Zeke... who uses Ryouga hot-headed state against him with a simple aikido throw and a 'boost' of wind to hurry him along... through several walls. Tatewaki is impressed, but before he challenges, Lum shows up, scares the bejeezus out of him (ONI! AAAUUUGH!), and she offers him the bomb which he accepts, because Kuno is just unprincipled like that. Zeke recognizes the weapon, tells everyone to run like their lives depended on it (because they did)... but not PK. He thinks he can disarm the damn thing. Instead, he just cooks the damn thing off and lands himself in the hospital for an extended stay.
Bonus: Zeke finds out about what Lum did and knows that giving an Earthman such a weapon is a huge no-no. This bit of blackmail material in hand, he threatens Lum with the prospect of telling her dad. the only reason he doesn't (and thus rid himself of her entirely) is because he's been studying crime and punishment among the Oni... and suffice to say, it isn't pretty.
The NWC will attend at Juban, just long enough for Furinkan to get back up on it's feet (the school board isn't taking any chances in whether or not PK wakes up anytime soon)... but it's still long enough for something to happen. (I'm thinking of having one of the Senshi use that line that I see in someone's sig floating around here: "Did you do something rash?" "Yes, and it was GLORIOUS!") Later, when Soun and Genma receive the formal request to have Ranma and Akane transferred to the special wing at Mahora, they agree to go with it because they know that A) Zeke is there, B) weird shit happens around Zeke, C) It's a special training school - one perfect for the Anything Goes school.
To avoid total curbstompage, not everyone will be around at all given times. Sousuke and the MITHRIL elements will have missions to run. Ranma will have new cures for his curse to hunt down. Zeke goes on walkabouts. Negi makes trips into the Magical Realm with his students. Miyuki takes on a few missions here and there. Kodachi occasionally has Yakuza business that takes her out of town (she has to fill in for her father while he's out cold). Matsuri's needed for a mission at the SSA. And the Government is perfectly accepting of all this - the entire point of the school is simply to keep better track of these people and make sure they don't do too much property damage. Also, there will be Big Bads in combinations as well by this time.
As for Yomiko Readman, her domain is going to be the satellite library that is part of the Special Youngsters Wing... of course, she'll still make trips down there with the Library Expedition Team (hell, she'll probably become their Faculty Adviser). To her, the traps would just be training to help her keep her edge. Also, once she sees that the water is having some sort of preservation effect on the books she'll relax considerably. Reference here: http://www.mangafox.com/m...a/v02/c009/12.html It's preservation - books do not soak for fifty years and come out undamaged. Hell, even sitting on the shelf for fifty years it doesn't do them any favors.
As for the Cardian battle, I'll go for it. In fact, I've thought of a decent intermediate weapon for Zeke - they happen to give him a full survival kit for pilots that have to ditch their aircraft... minus the pistol. This means he's got a decent survival knife on him. A knife he can charge with his spirit energy and use to good effect on a Cardian. It won't be Usagi's attack by a long-shot, but it'll be better than the weak infrared lasers from the VR Arcade. I can see him taking down one or two Cardians this way with Lum's help, but once he sees what he's really up against... yeah.
And yes, Zeke is most definitely the result of a butterfly that decided (not) to flap it's wings at a particular moment. Chaos will be most displeased.