I agree with you that the F-150 is too tall, particularly in the bed. In fact, the current F-250 looks better than the F-150 in that regard, with lower bed walls. If I were to get a full size truck, it would likely be the F-250.
I just don't need such a big truck, as it would be a waste of space, capability, and money. I looked at the F-150, and even the F-250, but I still come back to the size, looks, cost and relatively good mileage of the current Ranger. I wish Ford would just update the current Ranger with EcoBoost engines, 6-speed transmissions, and a mild interior refreshening. The current Ranger exterior is just fine with me.
If Ford doesn't redo the current Ranger, I believe that Ford should go ahead with the F-100 and have various Ranger trim levels. All it needs is to be 85-90% the size of the current F-150 and it would not canibalize the F-series sales.
Come on Ford, don't just give this segment to Toyota and Nissan, as I think it would be a strategic mistake.