Following a manufacturer's recommendations gets you highly reliable negatives that print normal scenes at the normal paper grade at normal times.

Normal doesn't mean mundane, Kodak and the others have worked hard to make normal a very high quality situation.

Before you or I decide on changing away from normal development (time, temp, or agitation) we probably need to have a situation that's not normal that's pushing us that way. For example Ansel Adams used graded paper which made adjusting the negative important, but he also was meticulous about measuring the scene; changes in development were driven by real numbers not somebody elses preferences.

We also need to remember that adjustments don't necessarily need to be done at the film. Today, unlike in Adams heyday, VC papers are great and contrast is easily and nicely adjustable with paper grade.

I'd suggest starting normal and defining where you want to go from there.