Add an NPC to the game that converts Job Points and Mlevel

[Alhanelem]

No. Why even have different levels for jobs in the first place if you don't have to play them to attain them?
You want levels on a job? Play that job. Any conversion would have to be heavily biased in favor of playing the actual job over grinding on some other job. Otherwise, people won't use the job they love, they'll use the one that's the most efficient, and you'll see literally everyone playing that job and only ever using the others when needed for endgame content.

Hell, FFXIV even tried this with having an underlying character level that affects all jobs and people just found this confusing. It was depricated and removed in ARR.