I like Star Trek and I like Ranma so I have thought about writing a crossover involving the two series. Figuring out how to bring Ranma into the Star Trek universe is extremely simple considering things like time travel, Q, the Preservers, sleeper ships, holodecks, etc. This, for example, would work: Spatial anomaly opens up in engineering stopping the entire ship and spitting out Ranma. Ranma had been looking for another cure for his curse activated some ancient magical/technological item and somehow ended up there.
I liked the idea of Seven of Nine, but not the implementation. I did not like that she got paired with Chakotay. I did not like how the crew treated her. There is actually a lot about Star Trek Voyager I did not like. That is in part why I want to introduce Ranma into the series, basically so I can have him force a change in things, particularly in how the crew thinks.
I would like a Ranma/Seven of Nine pairing. As such, the first thing I need to set up is a reason for Ranma to be around Seven of Nine. This fic would be set shortly after Seven of Nine is brought on to the ship, a time when she had very poor social skills, and was sorely lacking in knowledge in many things (she did not know how to sit or eat because of her Borg upbringing). The means I'm considering using to keep Seven of Nine and Ranma in close proximity is to have Ranma's aura interfere with the ships sensors and more importantly the Bioneural gel packs (similar to how several aliens were affected strangely by the sensors and how some spores that Nelix acquired messed with the gel packs). To prevent his aura from interfering with the ships systems, a Borg technology is needed to neutralize the effects forcing Ranma to stay within a certain radius of Seven.
I want to use Ranma for this fic because he is significantly different than the other humans; in many ways he is more alien than the aliens.
I want Ranma to point things out that I thought about that never really seems to be thought about in the Star Trek universe (an example: Combadges lost, why don't they ever use sub-dermal tracking devices for emergency beam outs?). Simple solutions to complex problems they would not think about since they prefer complex solutions involving lots of technobabble.
I want Ranma to point out differences between his world (in some cases our world) like why are interspecies babies so easy to produce when chimpanzee have around 99% the same DNA as humans and they can't breed together whereas aliens that have evolved on entirely different worlds can. Ask why people do not have jet packs or power armor since both existed in his time (both are seen in the manga).
Things that will not happen:
Ranma suddenly knowing how the technology works (he will learn the rudimentaries, so as to function in that society but he won't know the details - basically he will be taught how to drive a car but not how the car works, how to do anything but the most common fixes for the car, or how to build a car).
I'm still just brainstorming and this idea is no where near fully formed. There are all kinds of details that this is lacking in current form and all kinds of things to add. Could have Ranma train with the Holodeck, have them build him a gravity belt, Ranma be like a supped up Jem Hedar/ genetically engineered person (in Enterprise the humans who were genetically engineered were resistant to phaser blasts), could have Ranma learn new techniques for example how to travel via warp speed without a ship (like the alien known as the Traveler did and taught Wesley Crusher in Star Trek TNG).