The body is capable is ridiculous feats of adaptation if it is given a good reason to adapt. That being said, it's all up to the individual as to what works best for them. I for one hated every single second with the ileostomy and would be loathe to ever go back to it.
I decided, from day one, to make this new organ of mine do exactly what I want it to. I throw ridiculous foods at it so that it can learn how to handle them. I hold it in way longer than necessary to give the thing a reason to stretch out (my goal is to get it to the size of a normal rectum because hey, there's room for it down there).
In the end though, everyone's different and you've gotta do what's best for you. I certainly wouldn't recommend everyone eat half a large pizza for lunch and a double quarter-pounder for dinner.