One of the main problems with a system like this that I would personally have, is that I'm a member of both groups. Whether I want to take it easy or speedrun some clears simply depends on my mood at the time, which is influenced by what's going on in my life.

Just got off a long shift at work? All I want to do is kick back and relax, run some casual dungeons.

Woke up, had some breakfast, and fully energized for a day in Eorzea? Let's get some speedruns rolling, friends!

Considering my life is extremely fluid, what I seek in any given run can hit polar ends of the spectrum within even a single 24 hour period. This system wouldn't know what to do with me, and my experience in the game would likely suffer harshly for it.