A notion that would result in legal chaos and utter uncertainty that two cases with identical circumstances would be decided in the same way. On a site that decries judicial activism, you're calling for every judge to interpret the law for himself every time, and undermine every decision that has come before.
The methodology of "first principles" is the methodology of science. Science corrects mistakes better than does the legal system.
As for "identical circumstances", that is a subjective judgement. There may be nuances and subtleties between two "identical cases" that are not always readily apparent. Most such classifications of "identical circumstances" are just attempts to cubbyhole things to make them more convenient to grasp. A sort of Mental shorthand.
I think there is something fundamentally wrong with incorporating the tu quque fallacy as judicial policy. This "Well he got *THIS* punishment, so I should get no worse" may produce a foolish consistency, but it is the hobgoblin of little minds which implement it.
On a site that decries judicial activism, you're calling for every judge to interpret the law for himself every time, and undermine every decision that has come before.
I'm calling for every judge to not allow "Precedent" to be a substitute for thoughtful deliberation. I constantly see the fallacy of bad Precedent, or badly interpreted precedent. (Such as Wong Kim Ark.) I see where Precedent is a set of ruts leading off a cliff because prior precedent was decided wrongly or badly, or subsequent interpretations of it construe it broader than they should.
Precedent can be a guide, but it shouldn't be the first tool reached for by the Judicial hand. That should be first principles and careful thought.