For what it's worth, I thought you handled Akane's name
change well. I agree that you didn't want to stick with
it in a tale of this length.
The only other thing you might do is downplay it a bit at
its introduction, for instance, have her adopt the new name
as an additional one, even at the cost of historical inaccuracy.
I don't recommend this; I just throw the idea out.
I did feel that the epilogue seemed a bit disconnected with
the rest of the story, at least at first. Once I was into
it, the humor and the counter-intuitive matchups were quite
welcome, but still a bit disconnected. Much of the material
would work quite well as a standalone "Twenty Years Later"
type fic, but little of it appeared to directly follow as
consequences of your main story.
You might consider making it clearer at the end of 4-2 that
Nabiki did strangle Oda; this would remove any expectation
on the reader's part that the epilogue will immediately
follow the main story.
Other epilog suggestions: Make it clearer that Kasumi is now a
Yellow Dragon (if she is) as a consequence of the events
of your story. Make it clearer that Ukyou is now Prime
Minister as a consequence (if it is) of the events of your
story. Explore the Shampoo-Akane-Ranma threesome a bit
more.
Don't know if this helps or not.