I'm fully up for this, although I think Obez may have the problem with my full opinion.

You must have something to gain for it to be properRP, IMO.

So yes, Hitmen should be able to kill mayors after being paid. He gains money.
Mafia can kill the mayor to remove his vicious and brutal gun laws. They gain freedom.
Gangsters can take the mayor hostage, even if they agree with his laws, and demand ransom. They gain money.

As long as the player or the job actually gains something from the mayor's death/capturing, I believe it's proper. Of course, the debate will then soon come to of what counts as a proper reason. Something along the lines of "omg i wanted ppl to think gangsturs r cool and make us famus" will eventually come into play, so proper reasoning guidelines will be required. However, I fully agree with the post.