At 12:10 AM 7/21/1998 -0500, you wrote:

In several stories, Nodoka has suggested that Ranma marry Akane but have
Ukyou as a mistress and claims that this is a fine old Japanese custom.  

Two questions: 1) Is the mistress an accepted Japanese custom regarded as
tradition?

That probably depends on who you ask, regarding it being an accepted
custom...  With men, it's probably a great idea, but with women, at best it
would be abolished, at worst it's something to hope never happens to them.

              2) If so, why doesn't Kuno consider the idea?  Then his only
decision would be the choice of which to marry.

No, his decision which of his two loves would be denied the honor of
marrying him....  His attitude would undoubtedly be that he could not
possibly dishonor either of his two loves, so he must marry them BOTH!
HA-HAHAHA!!!!!