The trouble with a divorce between club and international football is the clubs will run all over the international game, the non-European confederations in particular will suffer. They try to do that now, every chance they get. Without a body controlling both club and country football, I doubt seriously a player would ever be released for say, the African Cup of Nations.
The problem, as I see it, is not FIFA itself. It is the people who run it. They are very uncomfortable with the shift in power from international to club football where they can exercise less control. Add to this power shift the fact they are even more uncomfortable with the 4 of the biggest clubs in the world being situated in England. And even more worrisome for the pinheads in Zürich is the largest emerging football markets, Asia and North America, naturally gravitate to the English game. More treasure into the Premier league's coffers. More dominance of English clubs.
But instead of learning to live and grow with it, they fight it stupidly with such mad measures as this 6+5.