Nice strawman deflection, but...  

...the crux of my statement is the question, "Should we be extending this long anyway, crew or not?"

The FAA is sometimes subtle.  They actually give quite a bit of leeway to those (such as yourself), who want to push every boundary, but they indicate subtly that you shouldn't be doing it.  The distinction between Part 91 and Part 135 is one such way.  Under part 135 they indicate that paying passengers should not be carried beyond 14 hours pilot duty day.  They are indicating it is unsafe for the passengers to do so. The fact that they do not regulate your judgement under part 91 can only be explained as a throwback to the bold spirit of barnstorming, or something.  We children obviously need more observation.

In another area the FAA does this is in IFR departures.  Under part 135, the IFR departure minimum is 1/2 mile visibility.  Under part 91, there is no such minimum.  You can depart IFR 0/0.  What?!?  Are part 91 pilots more skilled than part 135 pilots?  No, the FAA just leaves room for you to kill yourself, if you're so desperately inclined.