I'm interested in what you find out. Though a bit new to ToC & I'll add my 2 cents :)
I see it as follows: the step/leap of considering the organisatioin from the perspective of left-to-right pipe/processes and a chain comes from Goldratt, who, through the dialogue of Alex Rogo and Lou tells us:
If any organization was built for a purpose and any organization is composed of more than one person, then we must conclude that the purpose of the organization requires the synchronized efforts of more than one person." . . . If we need synchronized efforts,” I continue, “Then the contribution of any single person to the organization’s purpose is strongly dependent upon the performance of others.” . . . “If synchronized efforts are required and the contribution of one link is strongly dependent on the performance of the other links, we cannot ignore the fact that organizations are not just a pile of different links, they should be regarded as chains.” . . . The important thing is you’ve just proven that any organization should be viewed as a chain. . . here. Since the strength of the chain is determined by the weakest link, then the first step to improve an organization must be to identify the weakest link.” “Or links,” I correct. “Remember, an organization may be comprised of several independent chains.” - (Goldratt, Eliyahu M.. The Goal: A Process of Ongoing Improvement (p. 332). North River Press. Kindle Edition.)
If we take the left-to-right pipe/process, rotate it 90 degrees anti-clockwise, that can be the basis of making it a value chain. Even the logic diagram of the P&Q question looks like a value chain - see bottom page at http://www.dbrmfg.co.nz/Bottom%20Line%20Measurements%20P%20&%20Q%20Question.htm
And what's at the top is what's of value within that context.
As for where to improve, TOC reminds us of the 2 prerequisites: to know the sytem, its goal of the system and the measurements. In Wardley Maps, the measurements and the goal (not only to state them but for others to know them too and embody them) are encapsulated in the list of doctrine/principles. Measurements are stated under the category, "Leadership", where we're to "use a systemic mechanism of learning (a bias towards data)", which allows us to "revisit the previous strategy in order to understand where we have come from, what was intended, what was actually achieved, and what could’ve been done differently." This is included in Phase 1 of the implementation. Guess I'm starting to see why 🙂
As for where to improve, and dealing with constraints, I'll have to think about it some more. But I it's related to Climatic Patterns too.