“If someone wishes to speak in his language about a new kind of entities, he must introduce a system of new ways of speaking, subject to new rules; we shall call this procedure the construction of a linguistic framework for the new entities in question.” 
The assertibility of S is fine so far; though what of the whole meta-statement? What is the meta-statement assertible according to? This? -
Meta-statement MS is assertible according to CS1, in which S is assertible according to CS1.
The following is assertible in CS1: “…” is assertible in CS1.
Again, here we have auto-reference, which was earlier applicable to the CS itself.
“The semantic ‘definition’ [of truth] is not a definition of truth, but a criterion of the adequacy (accord with our intentions) of a predicate for the concept of truth within a given system. ‘True’ thus becomes a predicate applicable by the rules of a system to sentences of the system…In pure semantics the conditions of the truth of sentences in a system need not be found outside the system but must be provided within it.”