'Among the several states,' has historically been interpreted very broadly, as you are doubtless well aware.

Yes, it has been; so broadly in fact as to render the constraint meaningless. Do you think that the Framers really intended such a broad meaning?

I think it is more likely that it has been intentionally broadened from its original scope in order that the Federal Government be able to exercise a wider range of powers than intended by the Framers.

I do not think that they intended such broad interpretations, any more than I think they anticipated industrial society. In regards to ERISA, it would be appropriate for us to also consider the intentions of those who passed the XVI amendment between ~1909 and 1913, which established the constitutionality of income tax, Congressional power to collect same (and set up agencies such as the IRS to this end), etc., and who had ample time to consider the relationship between this amendment and the rest of the Constitution by debating what sort of practical consequences might ensue.

While I don't always agree with the way the Supreme Court decides matters (and it has seen fit to reverse itself on more than one occasion), I like the system of using the court as the appropriate forum to try such questions, and of electing legislators and executives to develop or implement new rules where the existing ones turn out to be flawed. If you feel you have spotted a glaring flaw in the Court's reasoning, I urge you to write it up and circulate it as widely as possible.

How can you claim that the Framers were unaware of the possible consequences of industrialization when "An Inquiry into the Nature and Causes of the Wealth of Nations" was published in 1776?

Issues surrounding capitalism, the division of labor etc. were being actively discussed back then, and industrialization as we know it got started properly in 1789 thanks to the efforts of Sam Slater.

Besides which, the correct way to expand the powers of the Federal Government is by an amendment to the Constitution, not the liberal interpretation of existing clauses. The former is transparent & leaves room for public debate; the latter is the practice of political appointees who do not care for their expansion to be the subject of public scrutiny in advance.