Can a Constitutional Convention be limited in scope?
It depends on who you ask.
But first, the use of the term "Constitutional Convention" in this article is misleading (at least I hope that Rubio is
NOT calling for an actual "Constitutional Convention!").
I have to believe that what he was talking about is more accurately named a "Convention of the States."
It is the second route (found in Article V of the Constitution) that Amendments can be made to the Constitution (the other one of course being via Congress, the method that all other Amendments have been made). Note that the Ratification process for both routes is the same, ratification by 3/4th of the States (via Legislatures or Ratifying Convention). The methods differ as to how an Amendment is proposed (via the voting 2/3 of both chambers of Congress, or via the support of 2/3 of the States).
Article V
The Congress, whenever two thirds of both houses shall deem it necessary, shall propose amendments to this Constitution, or, on the application of the legislatures of two thirds of the several states, shall call a convention for proposing amendments, which, in either case, shall be valid to all intents and purposes, as part of this Constitution, when ratified by the legislatures of three fourths of the several states, or by conventions in three fourths thereof, as the one or the other mode of ratification may be proposed by the Congress; provided that no amendment which may be made prior to the year one thousand eight hundred and eight shall in any manner affect the first and fourth clauses in the ninth section of the first article; and that no state, without its consent, shall be deprived of its equal suffrage in the Senate.
Note well in this discussion, the second method, via the Convention of the States, has never been attempted.
If you listen to Mark Levin and many others in the
Convention of States movement, a CoS *can* be limited in scope (to only the discussion of the amendment topics submitted by each State's call). Obviously his book,
The Liberty Amendments, is a good source to read up on the overall topic.
For an alternative point of view, reference the work of Publius Huldah:
https://publiushuldah.wordpress.com/article-v/