Buying Mesos

Supposing there was a site that paid all its "gold farmers" to farm mesos legitly.

There isn't and never will be. Some pretend that they do to fool especially naive/gullible people, but in reality there isn't a single one. Getting mesos legitly isn't nearly as profitable, and in that kind of business that is all that is important.

Hacked items/meso is just as much against the rules as it has always been, so yes, that would be wrong.

Obtaining them from any legitimate source such as a friend wouldn't be wrong, of course.