First off, David, I have to thank you for the points that you have raised up
about this chapter.  A writer needs to hear from various objective views
when creating a story. 

One thing that puzzles me about how Amazon customs are normally
presented is that it isn't much of a matriarchy if every single
woman is married to a guy who can beat her in combat either because
he's better, or because she likes him so much that she doesn't
want to hurt him.

In the initial discussion of the Amazon laws dealing with the 
consequences of combat, the rules appeared to apply to outsiders.
The theory was, kill any superior outsider woman so 
she wouldn't strengthen your neighbors with her bloodline and 
skill.  Marry any superior outsider male, perhaps any male who proves 
superior so he would do the same thing for your bloodline and skill.  

First off, back to the Anime and Manga in the actual Ranma 1/2.

I don't think that the Amazon laws are THAT strict.  If they are, then
Cologne wouldn't have accepted LinLin and RanRan's defeat at Akane's hands
in the anime with such ease.  And the two would have to try and kill Akane .
. . which they didn't.  I think this law is merely a flexible devise to
scare off outsiders.  

Besides, while Shampoo claimed that she was law bound to marry Ranma, she
did allow Mousse to date her once (Manga 27), and Cologne said it was a good
thing!  The law seems as flexible as a ribbon to me when you are a woman:
it's the targeted men that get trapped.

Were we ever told that an Amazon CAN'T marry a member of her own village
without combat, just because she MUST marry an outsider male who defeats 
her?  

Actually, Cologne did held Mousse not valid for Shampoo's hand due to the
fact that he lost to her at three . . . but then again, I didn't think it
was an issue of the law as much as Cologne's distain for his lack of skill.  

Could the problem with Mousse be that having challenged her, he is 
thereby legally debarred from consideration as Shampoo's husband, 
(perhaps a law designed to prevent frivolous marital challenges?).

 The Amazons are WOMEN ORIENTED, as such, I don't think there will be ANYWAY
that they would have had LAWS to bound the WOMEN themselves to MEN that they
might not like.  Women, I think, can marry any man that she want after an
almost symbolic combat, for then she can either make herself win or lose at
her own will.  And even if she does lose to a man that she don't like,
there's probably a loophole somewhere for her to reject the guy, or village
fails as a WOMEN-in-charge type of environment  Shampoo, for example, take
advantage of MOusse's feeling for her to prevent him from marrying her.  

"Wong" has come up with a fairly sensible answer by assuming that 
males in the village who have no exceptional fighting skills are 
simply kept as concubines, but it doesn't really fit what we have seen
of Shampoo in the real series.  
It seems likely to me that under this system, Mousse
would already be Shampoo's concubine and reluctant ally in attempts
to trap Ranma into marriage.  

Actually, I think THIS confusion is my fault for not explaining clearly in
the story.  The way I see it is this: the woman DO NOT have to take a man as
a concubine just because he lost to her.  She CHOOSES her man, and as such,
only men that she likes will be qualified as her concubine.  Since she
didn't LIKE Mousse, why would she take him as anything? 

However, of course, in the context
of Ranko and Kaneda at least the depiction isn't internally 
inconsistent, which may be more important than whether it's
consistent with the main universe.  This is, after all, another
universe where Amazons may have different customs.

Well, hope this answers all the question on THIS part of David's C&C, and I
think I'll go the next now :)