The diagrams you shared show elasticity and spring back. Spring back works both ways, on firing it springs back inward, and on resizing it springs back outward. When the elasticity strength is exceeded without exceeding the tensile strength of the brass, you see a permanent expansion. If there is a permanent expansion you need to size the brass beyond minimum size and let outward springback compensate to make ammunition in the proper dimensions.
I get how metal works, I get how reloading dies work. However, your argument boils down to "there might be some brass out there that was so abused that the FL die just won't cut it." You cannot make that assumption without knowing the dimensions of the chamber on the OPs rifle and the dimensions of the FL die.
I've resized 5.56 brass that was fired through a M249 SAWs and 7.62 brass fired through M240 machine guns and so far even that brass has functioned very well, even in a Wylde chamber on a White Oak upper and a minimum head space Savage 10. In my experience, with a variety of ARs, a 308 Saiga and various bolt action 308 rifles, that a full length resizing die will make ammunition that feeds reliably.
I readily admit that there are rifles out that that will need Small Base dies. But until the JRLSH tries out the die he has, we will not know if his AR is one of them. If his isn't, then there is no point in buying a small base die unless he wants to feed his ammo into a rifle that DOES need a small base die.
Machine guns are awesome until you have to carry one.