Just a brief comment on the "predicament." For one thing, I'm an old-timer myself--62 years old, having started Greek in the Fall of 1952. Moreover, my teaching is primarily in Classical Attic Greek rather than in Koine, and I am not impressed by a lot of what I've read to the extent that I think the classical doctrines about tense have been dislodged. What I think MAY be true is that the older views of the present and the aorist were cast a bit too rigidly; I suspect also that Hellenistic influence of native vernaculars on the Lingua Franca almost certainly had an impact on the way Greek was understood, spoken, and written in the era of the NT. It may be, however, that these investigators are overly inclined to cut the understanding of Koine grammar loose from its historical moorings; frankly, I haven't read Porter, and I think that I ought to before I judge him. I've read some of Wallace and have mixed feelings about his work--in his advanced grammar I'm inclined to think he multipl
ies grammatical categories overly much in the endeavor to nuance the grammatical categories to match differences that are nuanced in reality only in the context of particular NT texts. The one point that these new grammarians are making which I think IS correct is that context of a construction impacts heavily upon how it is to be understood in any particular text. On the other hand, I suspect it's a mistake to attempt to reformulate the understanding of the constructions unless the nuanced distinctions in usage appear in significant quantity in statistical samples.