Well I think you had it yesterday. It all comes down to how you define the word "state" as it is used in Article V. I claim state means state legislature since that's what the word means everywhere else it appears in the constitution.
The fact still remains that the 17th was passed and is in force. So what do we do now?
When I said it was a red-herring argument, I meant that if you are saying that the compelling argument to sway states to join in an Article V proposing convention is that the 17th was unconstitutional in the first place via the suffrage consent clause and should be repealed on those grounds, that's a very narrow and esoteric argument to make. You will lose many people in explaining the nuances of that position.
I always thought that the easier sell was to say that it eliminates costly elections, it gets a large chunk of money out of politics when the elections are eliminated, it forces the Senators to pay more attention to their state interests instead of party lobbyists, it forces the people to pay more attention to whom they elect for local offices, it gets the states back at the federal table.
-PJ