Jean de Rochefort
Triangle=The lower points represent uke and sh'te's points of contact with ground while in midst of attack/defense? The upper point represents their connection upon contact?
Circle=Uke and sh'te create a circle with the technique?
Square=Upon completion of the technique, uke and sh'te return to where they should be naturally? Each with their stability of two points represented by their corners?
From my own perspective I would caution against such ideas. If you analyze the way you have structured the interaction both uke and shite are equally balanced in each geometric figure. You even posit an ending in "square" where each has the "stability of two points." In other words an aikidoka has gone though an interaction and nothing has changed. What is the point of that?
You posit a triangle in which two persons have formed a stable arch-like structure. At such a point neither has any advantage and most likely a stalemate will result. Same with your idea about the circle.
I would recommend structuring your thinking into models in which you are the dominant component.