"Just do anything for a year"
As someone who has recruited new graduates for graduate schemes / entry level graduate jobs, I would caution against this. A year of doing non graduate work will make him look, on paper, like someone who either
a) couldn't get a good graduate job, and is hence the dregs of the crop (so why should I take him if so many others have presumably rejected him?)
b) couldn't be arsed to get a job (so am I going to struggle to motivate him?)
Either way, it's not a good look. Especially for someone wanting a place on a competitive graduate scheme. I have seen people who I know personally take a post uni gap year and then find that they are struggling to find a graduate job the following year, when they are competing with other fresh graduates.
I did once have to do a graduate recruitment round in January, for reasons out of my control. The quality was, overall, dire, because all the good ones had been snapped up months ago (though the one we finally took turned out to be a rough diamond who didn't interview well but was surprisingly competent).
I would strongly advise that he either takes a masters starting in September, or cracks on with finding a graduate job pronto, for the sake of his career.