I've seen WDW do this - once. On New Year's Eve two years ago, MK's walkways were TOTALLY structured. Everything was one-way paths and it was strongly enforced. Now, it made for roundabout routes and longer distances between two areas but traffic kept moving. Yes it was a packed but you could move and while it was a bit inconvenient, it beat being smooshed into a seething, unmoving wall of people. Simply put, it worked.
Compared to this past holiday season...we were there on Christmas Eve. Tom Staggs can brag to media all he wants that FP+ allowed them to "accommodate" 3,000 more people in Magic Kingdom but having been there, that's some serious bull$@#%. No one was "accommodated" in the slightest. With ZERO crowd control and the backstage bypass not even open, there was a couple hour period between parade and fireworks where you literally could not get to the exit. It was a shark feeding frenzy. It was so bad that Love was so disgusted he still doesn't want to go back. (And WDW is somewhere we've both loved since we were both kids.)
If WDW wants to control crowds and flow, they can. But if they chose not to, it's just going to be even MORE of a disaster with even MORE people trying to cram into the expanded Hub area.