An idea I've been thinking on for quite some time, for the old classic; A Ranma 1/2xSailor Moon crossover.
Set in the Sailor Moon anime primarily, with some minor changes. Trying to decide a good place to place it in the timeline. In placing it between which arcs and such, and then subsequently how to procede through the rest. All I know, is I most likely want to have it before SuperS. The minor changes I mentioned just refer to using a couple elements from the manga/Crystal, partly refering to Mamoru, in using his manga/Crystal age, as well as giving Tux his attack. Other ideas from the manga may be borrowed as well, but thats undecided at the moment.
Anyway, basic beginning excu-uh, I mean premise to start, thus far, has the Tendo residence completely totaled, and thus the Tendos and Saotomes decide to try and get away from the chaos of Nerima, and end up moving to the Juuban ward. Primarliy will be "Sailor Moon setting" focused, but I do want chapters/plots/etc that are of a more Ranma 1/2" nature. Stuff ranging from Ryoga showing up, as well as Ukyo and the Amazons also eventually following Ranma to Juuban. An original story arc between two would be the first arc of the story, then deviations in following SM story arcs.
Now, while this is indeed going to have Ranma become a Senshi, it won't happen in the usual way, but actually rather indirectly. Now, Ranma will have been reincarnated from the Silver Millenium era, but not as someone who was a Sailor, but as a male who like Mamoru/Endymion, possessed a Sailor Crystal/Star Seed. Now, not the most original choice, but going with Sun, what with still being an obvious choice since its one of the few celestial bodies of our solar system not used in canon, Ranma would be whom I am tentatively calling "Solar Knight". But because of his curse, and the nature of the crystals, in his girl form he can become Sailor Sun. For Solar Knight/Sailor Sun's element, going with light.
Now, with all that said, there is some ways that some less overused stuff can be inserted. One such possibility is that rather than being from the Moon, he could be from the Earth Kingdom, and would be a warrior who served Prince Endymion. And much like Endymion/Mamoru.
Next up, another thing to be included is exploiting the fact that this is a crossover, and bringing in some Ranma elements to Sailor Moon story. Namely, a thing that will happen, in some manner, Mamoru will become cursed, and with the same curse as Ranma. Which means that, much like Ranma will be able to turn into Solar Knight and Sailor Sun depending on which form he is in, Mamoru will gain the ability to become Sailor Earth in addition to Tuxedo Mask. Sailor Earth's powers will be plant(really, just roses) and earth based.
As far as I know, this idea is rarely explored, if at all. But I will freely admit there are many, many Ranma/Sailor Moon stories I've never read. Regardless though, just something to add something more to this.
Moving on to another non-canon idea, using more up to date knowledge of the Solar System, we've got a couple of more (dwarf) planets now. Key one being using Eris for a Sailor Eris, and leaning towards Akane. Issue there is that I need to come up with an adequate background and history, and then a power set. And then the best way to integrate it into the story.
The other two, I am undecided and unsure on for whether or not to even bother using them. Partly out of bias because 1). They don't have names of roman or greek god origin and 2). "Sailor Makemake" just doesn't sound good to me.
Next up, one of the ideas that was pitched by a friend has pitched is the use of the Shitennou, and going with an implementation of the manga/Crystal version of them as having served Endymion in the Silver Millenium. Particularly, while my friend whu suggested this is a fan of the Senshi/Shitennou pairings, I just like the idea of Mamoru having a team of his own. Also offers more male characters for the cast. A plus of this for storytelling purposes, gives Mamoru more to do and more purpose, which dwindled in the old anime especially. Also works if the possibility of Ranma's past life being from the Earth Kingdom is used.
Now, with this, I'm unsure of the specifics of how I should go about doing this, having a couple ideas. The first is that since in the 90s anime, the Shitennou were much different thanthe source, I could go with the Dark Kingdom versions were copies/replicas/clones/etc created by Beryl, and that the real ones that were Endymion's knights were reincarnated but haven't awakened to their past lives and living normal lives. One appealing thing about this is that I could use it to, since Takeuchi gives us age ranges for them, having Ranma go to school with the reincarnated Jadeite and Zoisite, prior to any of them having their past lives memories awakened.
Another potential thing is that the four were the originals but severely brainwashed, and were revived at the end of the first arc with the Silver Crystal like everyone else was and have been going about normal lives.
And with all that said, the other reason I'm posting this idea here is I really would like help more than anything. While I really do like the idea, I am not that confident in my own abilities to write this. Not to mention the whole blank area of still working out the plot. And while I do have some ideas on character interactions, ultimately, there is still that to also work out.