For the former, maybe a prophet of sorts to
insure that future would be better somehow by his
existance? For the latter, perhaps a devil posing as a
human to spread dangerous chaos that is barely
disguised as a comedy? Just a thought that occured to
me while reading it.

Interesting idea. I would never have thought of something like that
myself.

Miko did something resembling this, but in short form,
with "Soul of a Samurai" where Ranma _is_ a foul sorceror who
has imprisoned the pig-tailed girl for nefarious purposes.

This fic could have built on that idea.