Why do we have an unused constitutional safety mechanism sitting in plain sight, and why has Congress never seriously built the institution the amendment explicitly allows it to build?

I keep coming back to one weirdly under-discussed line in the 25th Amendment. Section 4 says the Vice President can act with a majority of the Cabinet **“or of such other body as Congress may by law provide”** to declare that a president is unable to discharge the powers and duties of the office. That “other body” has basically never been tested. So here’s the question: why has Congress never seriously explored creating one? Not “a panel that removes a president because people don’t like him.” That would obviously be dangerous. I mean an actual statutory body with strict standards, transparency requirements, medical/legal expertise, bipartisan appointment rules, and a very high threshold. Because right now, if a president starts behaving erratically, making serious factual mistakes, abusing presidential influence, or showing signs that raise legitimate questions about whether they can safely perform the job, the practical mechanism depends heavily on the same Cabinet members whose careers may depend on that president. That seems like a structural weakness. And before anyone says “that’s what impeachment is for” — impeachment deals with misconduct. Section 4 exists for **inability**. They are deliberately different constitutional mechanisms. The amendment itself seems to anticipate that the Cabinet might not always be the appropriate institution to make that determination, which is presumably why Congress was explicitly given the power to create an alternative body. I’m not even arguing that such a body should remove Trump, Biden, or anyone else. I’m asking a more basic question: **Why do we have an unused constitutional safety mechanism sitting in plain sight, and why has Congress never seriously built the institution the amendment explicitly allows it to build?**

And more importantly: what would a genuinely abuse-resistant version of that institution actually look like? Because if the answer is simply “we trust the Cabinet to handle it,” history should probably have taught us by now that designing constitutional safeguards around people voluntarily acting against their own political interests is not much of a safeguard.