I’ve been having a very long discussion with Luke about this on FB & the forum. I’ve settled on:
aionios = “of an undefined time period” = eonian
aion = “undefined time period” = eon
From the context you can find out information about eon, but eonian simply indicates that something occurs within an eon. This actually turns out to be a much more consistent translation (which is why it’s used in the Concordant Literal Version) than “eternal”, which can’t be consistently used e.g. Jonah time in the fish, stone walls & prison sentences in Josephus, occupation of Canaan, etc. See m.katabiblon.com/lexicon.php?lem … E%BF%CF%82 for more examples.
I agree with your excellent list of passages which I think makes it clear that aionios can’t be translated “eternal” without introducing many contradictions. It makes me sad that some people prefer to change “all/everyone/world” to mean “some”, rather than change “eternal” to mean “eonian”. It’s especially odd because, as far as I can tell, the only doctrine that is lost is ECT/P. i.e. God still has no beginning or end, the life with God still has no end, etc.