Honestly, I think Disney shot itself in the foot when it came out of the box with 3 pre-booked FPs. Anything less now will seem like a retraction, even though at Epcot, you are really only getting one that is useful. I think a better system would have been to allow guests to book one per day in advance. That way, they could have "locked in" their "must do" attraction, and then left the old system in place, even if that meant replacing the operations of the old system with a digital system. In other words, other than your one advanced FP, all others would be booked while in the park with no restrictions other than a limit of how much time must pass in between your selections. If they had come out of the box with this system, it would give the appearance of giving guests a huge benefit that they never had before without mucking up a system that was actually working. And to the people who would respond that 50% of the people weren't using the old system, I would say that once people got the opportunity to pre-book (just as they have now) it would familiarize them with the system such that they would have used in upon arrival. There is no reason to think that the current system is educating people on its use more so than what I would have done.
Edit to add: And instead of "Lock It In", my marketing campaign would have been: "What's Your Disney Must-Do?"