Actually, this idea of Kyhdin's could be taken several steps further
than just with a regenerative nanny. One could not just use the Ami
surviving the Fall idea though. Think of what a genius could do in
terms of preparation in the intervening time. Highlander with
magical powers. Not to mention how powerful she'd become. If she had
all that time to hone her powers, she could take on Kunzite alone.
One, Sailor Mercury survives the Fall. Her body either stays at
the same age, or she has access to some form of rejuvenation. Having
to wait for the others has caused her mind to collapse after a few
centuries. After which she undergoes 'life cycles'. She lives a life
until a certain point when her mind is incapable of dealing with it
any more. Her mind shuts down, her body undergoes rejuvenation and
instinct make her start a new life in a new place with amnesia.
Each life lives differently and brings a new perpective. This carries
on until the start of the series.
Becoming Sailor Mercury however, has awakened her past lives. Ami
basically has to compete with them. While she may be the dominant
personality, the others can distract her with their voices, or even
take over when she is vulnerable. This might both be useful
(warrioress in fights, healer after, understanding the experiences of
other, personalities at various time periods in history class.) and
detrimental (heartless assassin, seductress, psychopath, selfish
brats). How she deals with the problems they cause, reassimilate
would make a great story.
For even more trouble, have the Silver Millenium personality awaken.
That one has a completely non human mindset and thinks in a way
similar to the DK. Obeys Princess Serenity ONLY, she is a danger to
pretty much everyone else, including Usagi. Sooner or later, a
showdown has to occur.
On a slightly less dark note, have Ami die with the rest. She gets
reincarnated with the rest, something goes wrong. Her previous
personality is awakened, or for Kyhdin's idea, Rehka gets
reincarnated as well (Regeneration only goes so far). This could be a
result of trauma, badly cast magic, accident or overstraining her
powers or my favorite, Sailor Moon hits her with her tiara in their
initial meeting. Ami will not be aware of her second
personality at first. This could get better with her not even knowing
that she's Sailor Mercury. The other personality is in control of it.
Lots of stress is the result since she begins to lose time. She
awakens in places she's never been, maybe even with injuries. The
other Senshi may not be aware that someone else is in control when
Sailor Mercury is in action. Or they might be forced to keep it a
secret from Ami. All Ami knows is that she's compelled
to hang out with them.
Hope to see how this idea turns out. My muses have promised to do
their Akane impression if I even start another fic.
Hope this helps,
Stardragon