One way to keep this story from getting completely out of hand would be to
reverse your initial take on Akane.  Instead of using fanfic-convention
Akane, who would stay consistently furious at Ranma for the whole day and
probably dissolve the engagement, use the manga's
worried-about-Ranma-and-occasionally -perceptive Akane.

This Akane (i.e., the one from the initial Hinako story, the single fiancee
who did NOT go overboard about Ranma's apparent chasing of Hinako) might do
either of two things:
	1)  Conclude very quickly that Ranma is under a spell, and spend the
rest of the story trying to cure him, using various means, or (my personal
favorite, for this story:)
	2)  Remember Ranma's trial speech and the April 1 date very quickly,
and realize Ranma is putting everyone on.  You might have her notice the U-Y
manga, for instance, possibly by wild happenstance, and set herself up as
Ataru's most accustomed target positions, putting herself where Ranma will
HAVE to kiss her.  If Ranma DOES ask girls to tea and/or praise them
excessively, she might comment on how he CAN be nice to girls when he wants
to be.

Using Akane in this way gives you your damage control mechanism after the
day is over, as most of Furinkan will follow Akane's take on the day (and
Akane is the only one Ranma cares about anyway).

You could have some fun putting yourself and Shampoo into a T-M "Night
before the Carnival" shougo manga scene, where the two of you are obsessedly
reading U-Y manga, looking for ways to get Ranma's attention.  This might be
a nice scene to end on that night, neither realizing that Ranma won't be
behaving that way in the morning.

I agree with Gary about the trial.  As is, it's too long.  Either cut it, or
make it funnier (funny always works to justify material).  You could have
yourself take the stand and (given a small bribe by Nabiki) spin a tale of
being all alone with Ranma when he got out of control, vividly fantasizing
all the while.  Then, later, Ranma might think to act the scene out, as
revenge.
You could always have Nabiki call Happosai as a defense witness.