Etruscan future tense?

Carrying from my previous post, I've been thinking about tense and the workings of Etruscan grammar. Generally in world languages, I notice a tendency for temporal concepts like past, present and future that we find in verbs to be expressed respectively by ablative, locative and lative markers taken from nouns.

For example, in French, one may hear the phrase "Je viens de..." to express an action that is just completed. So "Je viens de laver la vaisselle." (literally "I come from washing the dishes.") expresses the idea that in English would be "I just finished washing the dishes". Thus a construction with an ablative meaning is being directly used for a past tense. Likewise even in English, we may say underlyingly lative-like constructions such as "I'm going to study now." to indicate an action that's set in the future. "Coming from" for past, "being at" for present, and "going to" for future. It's a pretty neat pattern that makes one wonder about how our brains fundamentally process space and time.

Returning to Etruscan, we have this construction in -eri (ie. -e [locative case] + postposition -ri 'for, to') and I've been questioning what to make of it. If the construction is taken literally, it may be described as an optative or necessitative as in "one is to X → one should X, one must X". On the other hand, it's quite natural and conceivable that it could have developed into a future tense and so perhaps we should translate it as "one will X". I find that oftentimes the semantic differences between future potential on the one hand and future certainty on the other are blurry in any language. In the long text of the Liber Linteus, I can translate the many verbs in -(e)ri into English either as true futures with "shall/will" or as necessitatives with "must/should" and still get satisfying results either way.

I also ponder on how the Etruscan verb is constructed and notice that, ignoring constructions in -eri for a minute, verbs obey a certain order of suffixing such that any mood markers come first (eg. mediopassive -in-), followed by aspectual markers (eg. perfective -ac-) and only finally by tense markers (eg. preterite -e). This perfectly explains forms like man-in-c-e '[it] has been left' (found in TLE 398) from the root man 'to remain'. However what do we make of -eri within this master plan then? If we explored this route of reasoning, we might then say that there may have come to be not just two tenses in Etruscan, past and non-past (as I've been stating up to now), but rather three tenses: -a (present), -e (past) and -eri (future). Is it feasible?

What holds me back from adopting this three-tense model just yet is the presence of eniaca in the Pyrgi Tablets. It resides in the closing sentence: Itanim heramve avil eniaca pulumχva. I interpret this verb to have a future meaning of "will have lasted", correlating perfectly with what is expressed in the Punic portion to the effect that the age of an erected temple statue "shall be as many years as the stars above". The perfective in -ac- conveys result or finality but, unlike the Bonfantes and others, I assert that verbs ending in -(a)ce are composed endings consisting of this perfective marker -ac- plus the preterite -e, to form what should be more accurately described as a perfective past. Judging from a form like eniaca then, and according to my model, -a must convey not only the present tense, but also the future tense as well (ie. -a must be described more generally as a present-future or non-past marker). So it seems to me that -(a)ca marks a lesser-used "perfective present-future" that occurs this one time.

This is one argument I can think of against just assuming a separation of future and present in this language as we find in modern European languages. This simpler two-way tense distinction surfaces elsewhere in some unrelated languages like Hittite and Proto-Germanic.