Licensing only works if you have to be in a certain jurisdiction to operate in it. Given that more "journalism" is online, if Murdoch or the Barclay Brothers or whoever don't like the restrictions of your licence, they can just employ journalists somewhere else. If they need boots on the ground, they can employ independent contractors.
How do you prevent independent journalists selling pieces to certain outlets without unfairly placing the burden on the journalist? Is it a list of proscribed publications? How does a publication get on the list? What happens to all the "good" journalists who work for an organisation when it gets put on the list?
What, exactly, is a journalist? Does it include columnists who write opinion pieces? If not, how do you prevent an outlet from running more and more "opinion pieces" masquerading as news? If you get defrocked for doing something your employer considers highly profitable, they can just rebrand you as a columnist.
What does it mean to be licensed? What does having a licence allow you to do that you can't do without one? Is this your "press pass" allowing you to ask questions at briefings? There have been cases recently when this has been revoked on a whim. Is it just to get a byline in a printed newspaper? Again, they can rebrand unlicensed journalists as runners, and print the piece under the name of a real journalist.
Journalism is not a terminal career like medicine or law. If you get thrown out of one of those professions, you lose your livelihood. There is nothing else that you are as well trained for that pays as well. You have to start at the bottom of something else. Most journalists are not particularly well paid. Former journalists can earn as much, if not more, writing press releases and advertising copy.