The first part I can't agree with. If a term limit, for example, is added to the constitution, it would not be able to be deemed unconstitutional. We see this at the state level with the Federales thwart the people in a state with federal law, but if something is clearly stated in an amendment, it is therefore part of the constitution. Your second part is definitely true. They federal leviathan will do all they can to ignore, thwart, and mutually act to get around new additions. Anything added would have to be written with proper legal implications so it cannot be twisted...and it must be written so it is easily explained and understood by all people.
The only argument I see against the Article V is the liklihood of actually getting amendments though the process and enacted. It's a long road. Otherwise, it makes all the sense in the world to proceed.
Thus, both nullification AND COS are needed. Might as well start going the COS route now, as we are talking many many years to relief.