Apparently there is a dormant amendment floating around out there that would
re-legalize slavery. If there is no deadline and states can't rescind their votes, there is a mechanism in place by which we could get this ratified. The KKK and other groups need to mobilize their members to pick up and move into a single state where they have enough voters to take over its government, like a racist version of the
Free State Project. They vote to ratify the Slavery Is Awesome Amendment. Then they move to another state and repeat the process, state by state. It would take a long time, but eventually they ram this through 38 legislatures. Obviously once the the pro-slavery people leave, each state would reelect sane legislators who would instantly try to rescind their state's ratification, but there are no takebacks so that won't work.
Like I mentioned earlier in the thread, I have no issue with the text of the ERA, and it seems to me that the 14th amendment already handles this. But it does seem to me that a rulebook where there is no ratification deadline
and states can't change their minds undermines what the constitution is trying to do, which is ensure a broad nationwide consensus for any proposed amendment.