Why just sensori-motor? : How about at times (esp. later ages) also simply memory capacities working just with that which is perceptual (or perceptual/attentional) ? Forget imagining your own 'schemes'/'schemas'; why not let the SUBJECT define itself [and refrain from needless hypothetico-deductive stuff and from the homunculus (for surely your way will inevitably 'need' "executive processes" or "meta-cognition" or some such -- though it is "allowable" in modern psychology to let vague 'social learning' basically "play" these roles, so you may emphasize that.)]?
Agency tied to sensori-motor? I can only see just simply that making sense (TO YOU) because FOR THIS PRESENT TOPIC, that is all psychology allows!! What?, is this a game? Come on, psychologists: You typically do not limit OTHER phenomenon involving episodic memory and other types of memory to a sensori-motor base. Nor in other contexts you do not limit phenomenological experience to some such thing. Rather it often is something with memory doing the clear contextualizing and nothing directly sensorimotor about it (not in your sense of the term anyway)!! (And, what do you know, your schemes are not needed!)
Broaden out and do what you usually do, in answering "other questions". Do that, and then [also, sensibly] posit some innate guidance involved in new levels of conceptualization** during ontogeny and you will be "with me"-- and with the likely biological realities.
Come on enactive, embodied, embedded people! You now have the eye-tracking tools. Why not use some new sensible imagination about development?
** FOOTNOTE: Where does the abstract thinking come from, in your conceptualization? Is it just conjured up internally in the mind? THERE IS NO NEED FOR THAT! (Read final note below.)
Since you seem to be into Piaget, you know that one type of equilibration referred the balance between assimilation and accommodation; the OTHER type of equilibration Piaget referred to was the balance between staying in the current stage-mode OR advancing to the next stage (he said this "occurred with maturation", but never explained this; I do in the paper referenced below!).
Article A Human Ethogram: Its Scientific Acceptability and Importanc...