I might disagree with you on number 1. Many guests DO like planning and scheduling their day at Disney.
Here's how I imagine it would work, and I should add that this is based on patents they filed in the past regarding Fastpass. It would be a tiered reservation system where guests staying at a Deluxe or DVC might be able to schedule 8-10 attractions for a given day, versus a moderate guest maybe only 6, and a value guest 4 or 5. Also, they wouldn't be able to plan their whole day, and they wouldn't be able to schedule more than one attraction per hour. Or, depending on which resort class they were in, the number per time slot would be restricted. Keep in mind too, that like Fastpass, not all rides would have this, so they couldn't exactly plan everything, but pretty close to it. Also, if part of Disney's reasoning in doing this is to encourage more guest spending, then they will by that respect, only allow so many things to be scheduled.
As for someone missing their time/window, it wouldn't throw off anything because all of their slots are designated for a specific time. If they miss one, they could always ask for a new slot (if available), or just have to face the fact that they missed it. Which of course, will cause some guest complaints. The other issue would be if the ride goes down, and how they handle it. Would they give out or re-assign new time slots for those guests who had them, or would they simply make everyone re-schedule. If this is done electronically, then it's easily resolved via the system and the guest is automatically given a new time. However, that doesn't guarantee that some guests won't get bumped. But then, that's how it currently works too.
Again, this is all just my own speculation, but I can see the groundwork for this being laid out.