I think what you're suggesting would work better as professions rather than a separate thing. The Magizoologist is already being planned to be added as a profession after Revelius. I think it would also fit the lore better because you don't just start learning Magizoology or Muggle Studies when you graduate; wizards would learn them at Hogwarts as they progress, which is reflected by professions being tied to player levels.
With your idea of adding an Auror job, I remember them mentioning in the Q&A that eventually there would be allegiance based quests (i.e. you could choose to be good and get quests by the Ministry or join the Dark Followers). From what I can tell, this sounds sort of similar to what you are suggesting.
At the end, you stated that it could raise the future potential of Potterworld because it gives Graduates something to do. I agree that Graduates have very little to do right now, and it is often extremely boring for me to play because I don't have any way to progress. However, I do believe that the Revelius Update will fix it to some extent. From what we know so far, it seems like quests will keep people occupied for the first couple of months. After that, it looks like trying to gather the best gear and brooms will be the goal. Hopefully, by that time there will be some kind of addition to the server. I believe it is about 10 months from the Exploration Update to the Revelius Update. Keep in mind that the Revelius Update is a huge overhaul of many key aspects of the server such as professions and spell progression, not to mention a gigantic map and over 70 quests. With that kind of timeline, I'm expecting the first expansion to the Revelius Update to be out within the first few months, before people become too bored. If consistent updates happen every few months, then I can't really see boredom becoming much of a problem. Currently, much of the dissatisfaction and dullness that Graduates experience is caused by the fact that we haven't received a major update in almost a year, so if there are more common updates it won't be as much of a problem.