A regulator assessing whether a firm is systemically important for a public good has no standard comparable to the one a banking supervisor uses for financial stability. Disclosure exists, but it is voluntary in most sectors, framed by the firm, and not written to be compared with anything.
This is the module where the honest answer is that the evidence base does not yet support strong conclusions. Naming that, and specifying what disclosure would have to exist for the question to be answerable, is more useful than a ranking built on data that cannot bear it.