While legislators are a group of spoiled functionaries, who knows what delegates would look like?
I guess I see the distiction you are trying to make, but seeing the lid lifted on the box that contains the Rule of the Proletariate makes me shudder with the first creak of the hinges.
You are saying that delegates are no more dangerous than Congressmen. That is perhaps true in general but the left is more vigilent in seizing opportunities to seize power than the right is in simply hoping it power can be kept caged up.
But due to a combination of the crisis of the time and the respect held for General Washington, Congress decided to let the work of the Convention go to the states for ratification.
Technically, no law was violated and all norms were followed.
Again, I'm attempting to show that a Convention for Proposing Amendments called to address one subject cannot become the "runaway" convention, driven by the rule of the proletariat, that you fear.
As to what a convention would look like in the makeup of its delegates, it would look like America. You might find that a fearful specter to behold, but I'm not all that worried. There is minimal damage that could be done in a single subject convention, and in the end the state legislatures (or ratifying conventions) would be the final judge as to what does and doesn't get into the Constitution.
The Framers set a high bar for amendment for a reason.