I'm going to respond to all your posts at once, and hopefully I'm not going to 
forget anything.

Re:  Jusenkyo Cures and the One-only Curse
Why did I make it so that only one person can be cursed at a time, and no one 
can be cured until the person that can be cursed dies (or is cured)?
The answer is simple - I wanted to have both Ranma and Ranko cursed at the 
same time, but have them oppositely cursed in girl and boy form.  However, 
this presented the problem in that if they knew where the "cure" ponds were in 
the beginning, then they would have tried to cure themselves, so in order to 
keep them cursed I made the cure exclusive so that it works one-time only 
(sort of like the onsen mix) for each dip in the pool.

Re:  Ranma and Akane
Why did I get them together so early?  Because I wanted to have them build a 
relationship in spite of them having sex.  A marriage isn't just what they 
have at the end of episode 1, and they know it.

Re:  Mixing curses
I thought that the curses only became permanent (in the original story) by 
falling into one of the pools (otherwise, why does the onsen mix work only 
once?)

Sorry about the shortness, but my internet provider has a five-minute idle 
cut-off time.

JK