I don't know. I felt that moving to FP+ rather than FP was unnecessary, but the powers that be felt it was necessary so people were locked into a specific park. Going to a 100% FP+ system for a number of rides will do an even better job of making sure people are locked into a specific park because there are plenty of rides people want to ride. Currently, a person might get FP+ for Mine Train, Space Mountain, and Splash Mountain. That only locks them in for those hours, though. By making Mine Train, Space Mountain, Thunder Mountain, Splash Mountain, Peter Pan's Flight, Haunted Mansion, and Pirates of the Caribbean FP+ only, a person would, in theory, book all of these for the same day, thereby locking them in to Magic Kingdom all day. Also, my family has noticed that FP+ makes it so we spend less time in the parks. We aren't going to stand in long lines and FP+ makes it so we are only guaranteed those 3 rides with minimal wait, unlike how legacy FP was. So, after our initial 3, we are more likely to leave. And, we are more likely to sleep in and not do rope drop at places like Epcot where there aren't many rides to begin with and not a big chance of doing the headliners more than once. So, if you go to a FP+ system for the majority of rides, a person will more than likely be locked in for a longer period of time at a park. Between rides, they are more likely to shop or eat. Those things are likely if the person is back at the hotel taking a nap or going for a swim. I honestly wouldn't assume Disney hasn't considered this just yet.
ooohhhh...not only that, but if they spaced out the rides far enough, you wouldn't leave the park. So what's left between those 6 or 7 FP+ only rides? Shopping and eating of course. Diabolical.