This is pure academic theory-crafting. Who is going to pay for this and how will it be financed? Even in the industrial space, it's simply not going to happen

This is pure academic theory-crafting. Who is going to pay for this and how will it be financed? Even in the industrial space, it's simply not going to happen given the costs of securing wrt the business value and relative risk aside from projects that have some sort of community/municipal/national "critical infrastructure" domain (think power generation) where a legitimate business case (think in terms of MARR https://en.wikipedia.org/wiki/Minimum_acceptable_rate_of_return https://en.wikipedia.org/wiki/Minimum_acceptable_rate_of_ret... ) can be made for safety and/or regulatory compliance future-proofing and a source of cheap 3rd party (usually government) capital is made available. There are also huge legacy IoT investments in capital inefficient low-margin businesses (think mining and ship-building) where this sort of "maintenance" and retroactively applying "defense in depth" makes little sense compared to wholesale generational migration. Nobody is going to do it until there's some sort of abrupt forced exigent existential externality applied to the entire industry (e.g. ozone layer depletion and refrigerants) and then they'll be a single mass-migration.