You may love the idea, but in order for WDW to make them functional in terms of reducing lines, it will need to be in the price ball park of the CLFPs. That's $25 per FP -- plus you have to do three days plus you have to stay at one of their most expensive rooms in that hotel. I don't think WDW could charge enough to make a full-day FP feasible -- a lot of these people coming would pay $400-500 without batting an eye -- people pay $600/hour (plus tip) for VIP tours. Even at a full load of 10 guests per tour, that's $60/hour per guest. With walking and FP lines, loading and unloading (remember, this isn't DAH; there are still crowds), I think it's hard to get more than three an hour, so $20/person/ride IF every person is going on every ride.
If they just sell full day FPs, in order for the paid FP to have the value it's intended, I don't think they could charge less than $500 each. So then you have the family of four's day at MK costing $2500 (you still have park admission). That's not great optics. Even at that, If they kill their VIP tour business and probably the CLFPs. And they end up with WDW being a place that only the rich(er) enjoy. And if they go much less, then everybody does it -- or everybody feels like they have to do it -- and the benefit is greatly reduced.
So I think it's one of those things that sounds really cool until you start thinking about how it would really work, and then the appeal to all but those with money to burn fades rather quickly.