Create a link to "Stable" firmware?

I think you're addressing all my concerns.

My concern is that it's infeasible to test a mass change from one version to the next. (That's more or less the "comprehensive test" I spoke of.) Since we have no access to most of the routers, and potentially they aren't even in service any place on the planet, we'll never know.

I will concede that there's no difference with a "stable" symlink/redirect - we wind up in exactly the same state.

The solution for either of these is for people who own that router to update the page to point to the last-working version.

Actually, you've answered my question - "Yes, we do have that protection." The script won't update a link if it's not exactly the right version. So a device that's stuck at 17.01.2 will never be updated automatically.

I agree this should become part of the standard release process. I will leave the implementation decision to people more familiar with that machinery.

Ahah! You can suppress those? Great!

I still remain uneasy changing hundreds of files automatically, but I cannot come up with a plausible failure mode that would argue against this. I consider this Solved, and updated the OP to reflect this. We can go work on more important things. Thanks.