The big disadvantage to that is how long it takes. 11 match weeks is ages and that could take anything up to 13 weeks with qualifiers and inevitable scheduling difficulties.
Also, what happened last time was that some teams just couldn't hold it together for very long and it became a pain for everyone involved trying to schedule matches, which were often quite tedious. I think the "qualifying group" system should do quite well, since it guarantees 4 matches for every team and no team is ever forced to play a match at a point where they simply cannot proceed regardless of the result.