Sure raiding and dungeons are fun. But why would i do this more than once? I play it once and leave. Nothing to reach anymore. Gearing is the reason people play it that long and the reason i like the game. Sure clearing heroic and ventruing into mythic is fun. But after the first time you kill a boss everything after is just for gear.
There would be absolute NO reason whatsover to do any other boss than the one you are currently progressing. None. Ever. If you have to reclear every week that would make it even worse.
You would take what is left of fun in the game and make it worse than it ever was. I think this is one of the if not the worst idea for the game i have ever read in this forum. Sorry...