If one looks to Norman French and Middle English as a typical example of intense linguistic contacts between two historical languages in order to understand better the Proto-Semitic and Proto-IE contacts during the Neolithic, one may notice that only a small number of verbal forms in French loans typically surface in English. For example, many verbs were simply borrowed from the presentive form (c.f. French (il) part vs. English to part). However there are also many verbs which were borrowed into English based on French infinitives (c.f. French rendre vs. English to render which fossilizes the infinitive ending in -re).
Given that, I start to wonder if maybe it would be more organized on my part to compare Semitic and PIE verbs according to only a few specific verbal forms. So I've been thinking about how to answer the question “If I were to pick only two Proto-Semitic verb forms as sources of PIE loans, which would I pick that would fit most or all of the data the best?”
Based on the handy Semitic Binyanim pdf, my answer at this point would now have to be: 1) the nominative-declined active participle of the shape *CāCiCu and 2) the nominative-declined infinitive of the form *CaCāCu. This could account for almost all Semitic verbal loans that pop up in Mid IE, if we assume that Mid IE speakers simply ignored vocalic length (i.e. interpreting both PSem *a and *ā as MIE *e), that MIE employed a fixed penultimate accent, and that the rule of Proto-Semitic accent by contrast was that it was to be either placed on the first available non-wordfinal “heavy syllable” (i.e. CV: or CVC) from left-to-right or on the initial syllable by default. Predictably, the irregular essive verb *yiθ (becoming PIE *h₁es-) would be an outlier from this general pattern and “to be” is a rather oddball verb cross-linguistically speaking.
So, I guess I need to update my SemiticPreIEloans.pdf document on esnips to reflect this. I hope that sounds a bit more organized than what I've been saying so far. Little by little, I'm gettin' there hopefully. Cross fingers.