Saw an intersting fanart pic...
http://www.toyboxarts.com/gallery/numbers/pages/tb10e.html
entitled "Dark Side of Small Lady"...
Caused a weird idea ...

"A Journel into the Darkside" (Working Title)
During the Wiseman/Death Phantom storyline, Dark Lady decides she
wants her own Prince at her side just like her mother, Neo-Queen
Serenity. To Dark Lady, Prince Diamond is a wimp... 
So she decides to go looking around for someone better.

A little time passes...

Dark Lady spots Ranma, whom she remembers from the Future/Crystal
Tokyo. I figure at some point, Ranma with Ranma's martial arts
abilities/skills and everything that happens to him, at some point he
becomes immortal and doesn't age... In Crystal Tokyo, he's known only
as "Sensei", whose the Master of All Martial Arts (and some mystic
arts too)...
No one tells Sensei what to do, not even Neo-Queen Serenity or any of
the Senshi. Sensei is a "Force of Nature," outside of the doamin of
mere humans. Either you respect Sensei as a person, or you fear his
Power. The Senshi that Sensei is, at least, their equal in Power and
that he, unlike themselves, is immortal, while the Senshi just age
very slowly...

Since the only other long-lived male is Endymion, whose married to the
Queen, the Senshi do not have many choices for long-term
relationship(s), so Sensei is the "target" of many of the Senshi's
libido and reproductive dreams... <eg> Of course, women have been
throwing themselves at Sensei for so long, that he's immune to them,
giving everyone the impression that no woman has proven herself "woman
enough" for him.

Well, Dark Lady decides to prove she's more woman than any of the
Senshi or her mother by getting Sensei for herself. So she spends some
time in setting up Ranma...

Of course, the best Dark Lady can do is implant a black poison crystal
into Ranma. 

Realizing that she does not have an army or servents like most of the
other Sailor Moon villians, Dark Lady use the Timekey she has to
gather them by stealing them from the other Sailor Moon Villians, both
Past and Future. And sets them up to surprise Prince Diamond and
Wiseman to gain control of the Black Moon Family and its Power.

Of course, Dark Lady did not plan on her being "healed" by her mother
and being turned back into Chibi-Usa. Or that the "removal" of the
Evil in her, also removes her evil plans she had as Dark Lady.

Because of the Black Poison Crystal, Ranma turns evil-like... He won't
take any of the crap that he does in canon. He pays the others paid in
spades. Kuno, Ryouga, Mousse, Akane, and Happosai are sent into
Hospital's Intensive Care Unit. Shampoo and Genma are locked in their
cursed-forms. Photos of Nabiki appear in various shady publications...
as well as the fact, that others that Nabiki have "wronged" can show
her their displeasure since Ranma will not protect anymore. Kasumi,
Kodachi and Ukyou are reduced to nothing more than plaything for
evil-Ranma.

Basically, evil-Ranma takes over Nerima...
... thus setting off Dark Lady's plans.

So the Senshi must face an evil-Ranma and Dark Lady's plans. Plus,
evil-Ranma wants his Dark Lady back...