If I was able to re-design, or reconfigure, the human body and the way it works, one item on my agenda would be this: I'd have the digestive system and, um, refuse disposal system, work so that the farts came after expulsion of the fecal matter. So you would shit, and then you would fart. The farting would then help dislodge some of the remaining, um, matter, making clean-up a bit easier. Kind of like a wind-bidet.
The way it mostly works now, farting followed by shitting, is, well, ass backwards.