The neat thing about keeping a blog for any length of time is that one can see how old one's ideas are and how one can reuse past ideas to eventually crystallize a thought into something more detailed and polished. Almost two years ago, I had talked about stages of Pre-IE with subjective-objective contrast which was in turn inspired by Allan Bomhard's words on Pre-IE in his idea-packed book, Indo-European and the Nostratic Hypothesis (1996). While I will never be a fan of current Nostratic reconstruction for its lack of scholarly rigour and poor methodology, the idea of a subjective-objective contrast ultimately linking PIE to Uralic stuck in my mind for... well... more than two years!!!
It's sadly only now that I realize how much of an impact these ideas can have towards finally understanding PIE grammar completely. COMPLETELY! I'm going to now assert the following premise for the sake of discussion: PIE *itself* still retained a subjective-objective contrast and this is what lies behind the suppletive *mi- and *h₂e conjugations. To sum up, "objective" is a conjugational form that marks verbs as "object-focussed" while "subjective" implies "subject-focus", as in modern Uralic languages like Hungarian or Nenets. For example, any action effected through one's own body parts can be automatically considered "subjective" such as "to know" (via one's brain), "to see" (via one's eyes) or "to feel" (via one's physical skin or by one's internal emotions). Other subjective verbs might simply be subject-focussed arbitrarily such as "I hunt" (naturally implying that animals of an unspecified sort are being hunted, and hence that the action is unavoidably transitive despite a lack of expressed object).
It looks to me that what I've previously mused about the origin of the 1ps pronoun is yet one example of evidence in favour of a subjective-objective contrast in PIE itself. If *h₁ég-o-h₂ (or perhaps more accurately *h₁ég-o-h₂e) is originally a subjunctive verb form meaning "(as for) my being here" and if Jay Jasanoff is correct in deriving all thematic verbs from the subjunctive, then the unique subjunctive 1ps ending *-o-h₂e, which later becomes the "thematic 1ps" familiar to avid Hellenists and Indo-Iranianists and which so self-evidently borrows at some point from the *h₂e-conjugation (but curiously only in this 1ps), is indeed a relic of this subjective-objective contrast. Afterall, one's thoughts (and one's potential expressed so specifically by the 1ps subjunctive, eg. "I would go/I will go") simply imply subjectivity, making the replacement of an earlier Pre-IE 1ps subjunctive *-o-mi, the otherwise expected form, with this new subjective ending all the more natural.
Again too, the use of the specific *h₂e-conjugation as a basis for the middle endings (*-h₂ór < MIE *-xá-ra, *-t(h₂)ór < *-tá-ra, *-ór < *-á-ra, etc.) is simultaneously also explained best through this paradigm being used to express the subjective rather than stative or perfective. The result of the action isn't important, neither is any implied state, whether arrived at by an action or not. What's rather most important to the *h₂e-conjugation is that the action and/or subject is the true focus and not the object which remains comparatively less defined or even entirely undefined (ie. less important to topicality). Considering that the intransitive verb, and the subjective forms that may spring from it, can in turn develop into an aspectual perfective (aka punctive, punctual) is a delicious bonus too since it now helps to link this hypothetical "Indo-Anatolian" system with the later system of durative-aorist-perfective in the later "Core PIE" from which non-Anatolian and non-Tocharian dialects sprang such as Indo-Iranian and Hellenic (Greek).