Did you mean to say practical rather than theoretical? (it's not relevant to my argument either way)
But, again, there isn't any disagreement on this issue in the populace of any state. 50 states agree marriage means a man and a woman. Heck, all the history of Western civilization says the same.
Then why not just block the Court and say a State alone decides the matter?
Why should an amendment leave this matter open for debate?
If the goals are to have a specific standard for everyone in the US and to remove that power from the States, then it shouldn't.
I'm not sure I see your point. I see it conceptally, but not tactically. You seem to be going to great pains to preserve the right of a state to define marriage differently than the others. But among the people of the country there is an overwhelming consensus (even in very left leaning states) that marriage isn't something up for that sort of decision.
It sort of reminds me of that scene in Monty Python's "Life of Brian." In the scene, Stan wants to be a woman so that he can have babies. After some argument and confusion, they agree that he can't have babies because he doesn't have a womb. But they will fight for his right to have babies.
Fighting for the right of a state to redefine marriage reminds me of that.