The driving force behind these arguments is always an attempt to protect the sanctity of the judge.
This is quite excessive a criticism. If I felt exegetically compelled to take the
literal human-sacrifice view, then I should agree in advance that the content of the book of Judges (and not that book alone in the OT!) would more than justify that conclusion. Yet, there's a decent cumulative case argument that killing a human being was not Jephtha's intent, this in spite of the story-arc of the book.
You could begin or end the argument with Heb.11:32. All the men of faith listed in that verse (and in the rest of the ch.) are certainly sinners and great sinners; but if nearly the last word recorded on Jephtha's life was that he offered an abomination to the LORD as a thank offering--a faithless act, surely--he would be the oddest man out for choosing, in my opinion. Is it possible that the writer of Judges wanted to tell us that Jephtha (for all the good he did) was a partaker of the basest wickedness of the Canaanites most contrary to Israel's statues (Lev.20:2-5; Dt.18:10; cf.12:31)?
I suppose so, but it isn't obvious to me, mainly because the text is not explicit; but there is more. Num.18 speaks about the dedication of the first and best of many things to the LORD, some of which went to the flames of sacrifice, some which was "reserved from the fire," all which was
herem, v14. And some things were redeemable, especially the unclean beasts,
which things could not be sacrificed on the LORD's altar, v15 (which was any altar, not just the sanctuary's). Evidently, substitution was permitted in cases where devotion could not be consecrated strictly by
olah. (See Lev.27 for regulation concerning dedication and redemption; note v11 where unclean animals are specified as sacrificially excluded.) And surely, human flesh was excluded! (cf. Jer.32:35, "...which I did not command, neither came it into my mind.")
Of course, these concerns raise the question of how dedicated Jephtha was to the Law of Moses. Did he know (or care) what was acceptable, or how things (or animals, or people) could be dedicated? Or who was authorized to perform sacrifices, whether ordinarily or extraordinarily? Earlier in Jdg.11, Jephtha makes numerous references to the sacred history found in Num.20-21. This is
prima facie evidence that he is at least modestly acquainted with the content of the Law of Moses.
I feel sometimes like the pendulum swings the other way, and we're more than willing to assume that the worst-case scenario is the most likely, and minimize what contrary evidence is available, in favor of proving depravity.