OK, it's again time to get all these ideas spinning inside my head out to be
someone elses headache,so here gomes, enjoy. 

1: Once again Ranma leaves to training trip and of course their parents send
Akane with him. Now, this wouldn't be so bad (considerening) and they
actually might come along, but then Shampoo and Ukyou deside to drop in and
the fun begins. 
  In some valley on the wilder parts of Japan all the girls get into
cat-fight (possible right after both or just the other appears) and get in
to a really close rance fight during which they all roll and drop in to a
spring that just happens to be there. Ranma, who is in his (her?) cursed
form at the time (possible reason or just the side effect of the fight),
appears just in time to see that they all drop in the spring and, seeing
that none of them seems to be able to swim for some reason, dives in to save
them; only to find that all,except Ranma herself, have grown much yonger
(four to six, you pick it) and that they all keep calling her 'mothter'.
  All this mess has called around near living hermit or monk (or both, you
pick it), who tells that the spring they all just were is legendary 'Spring
of youth' (or something like that) that will return those immersed to their
youth or (in this case) childhood (unfortunately in this case those affected
recain also much of their that time personality and that parts of their
memories will disappear to their subsconscious)  and that: a) luckily the
effects are only temporary keeping those affected on their current state
only few months, after which they will return to their true age and state of
mind with accelerated rate during month; b) for unknown reason it has
strange effect to those with Jusenkyo curse: it locks cursed persons in that
form they had when they dropped in during the time spring's effecting them
and those on their cursed form are unaffected by springs ability to turn
people younger. 
In other words Ranma has now three children, who keep calling her mother and
acting like it, on her hands (reason why all girls keep doing this is
simply: none of them has mother during this time and they subsconsciously
want to prevent this memory and following pain by ponding to first female
they have emotial pond, and ques who that one is) and they are very far from
Nerima.
  All the rest I leave to your own imagination, but here is wheve points to
think. Now after they have succeeded on returning to Nerima they have few
proplems, namely Mousse and Ryouga (and possiple Kuno), and the fact that
that all the girls refuse to leave their 'mother', also, how will their
puberty go: remember, it is compressed in only few days, and how will they
react when they are back to normal.

2. After one more big fight between Ranma and Akane he has, at last, had
enought and desides that it's time to do some serious thinking about all his
engagements, his curse and his life in general. To ensure that he has
possibility to do this without interruptions he goes to training trip
without more than leaving message where he tells that he's doing this and
doesn't know when he returns. 
  After finding this one out Akane gets one of the biggest temper tantrums
because he left without telling her and before she had forgiven Ranma. After
which she goes into deep depression (not one of Ryoga's level thought) from
same reason, and desides to find him out. The reason why she's very likely
going to succees on this is very simple: because she seems to have ability
to appear on place excactly worst possible moment on Ranmas point of wiev
it's pretty likely that she's able to find him on other times too when
seriously needed.
  Of course other peoples reactions are pretty obvious.

3. Well, this is loaned from someone else (please don't kill me if you
recognice this one), but what if, trought some of the Happosai's tricks,
Shampoo's spices or Genma's and Soun's tryings to ensure their marriage,
Ranma and Akane got telepathic link on each others minds and feelings. What
excactly would follow from that?

4. In the beginning of summer vacation Ranma decides (for some reason you
can pick) that it's definitely time to go to meet his cousin Ranma hasn't
seen for years. 
  Good thing is that his cousin lives way out of Tokyo so Ranmas fiancees
and rivals won't be likely to drop in( hah, just kidding).
  Bad thing is that this cousin is Masaki Tenchi, and he has his troubles
with girls too.

OK, there it is. Pick any you want and use as you see fit, it's no longer
under my responbility.
KK