...[ίδi] does not sound like an actual verb...
There are however forms like ἴδει, ἴδη, ἴδῃ, ἴδοι, οἴδει, which may be verbal forms. (Or even forms like ἔδει, ἔδη, ἔδῃ, ᾄδει - being considered here at least for their terminations).
... the time period is critical. After 200 CE ...
Yet, in the case of Luke, we are speaking of 60-70 CE; I wonder if this could be relevant in any way.
... "Koine ears"...
I wonder if the 'koine ears' of 200 BC could be assimilated with those of 200 CE. There was perhaps a continuous floating tendency, from few alterations at the beginning of koine era, to neraly what Modern Greek is today, by the end of it.
... such precision in definition is rarely needed or helpful...
Yet, every article or chapter on Greek phonetics would define with relatively good precision certain standards concerning pronounciation; precision is needed and hepful, I believe, at least at the level of teaching. My concern would be simply what to choose from the wide variety of pronounciation practices of Koine era. If we consider its beginnings, there are few alterations, probably generated by non-Greeks living in various places of the Greek empire, who adopted the language; by that time, those people were not to be considered 'native speakers', I think. I expect teachers of Greek in those times would stick with the old ways in their teaching Greek as a foreign language, rather than with the changes which continually entered 'the market' and altered the old ways of pronounciation.
Take these two examples of how some people pronounce the English language of today:
Such trends could very well be considered as a 'koinenisation' of English. Even though there is a significant number of teachers whose opinion is that in teaching a foreign language substitute sounds could very well be employed instead of some of the special sounds of the language under study, my opinion is that keeping up with the original is always more advisable. (Any language has but a few sounds that are really 'special' as compared with any other language).
As for Koine Greek, for any given period of time, if I have to choose between those who are bringing in new ways and those who advocate the old ways, I would always opt for the latter.