C(no3) is just the notes C and G. C7(no3) is the notes C, G and Bb. Is it valid to have a C11(no3) chord? Or would this just be referred to as some kind of sus chord (like C9sus4 or something)? Which is more “correct”?
Given the example of C11(no3), it's more likely to be called G-7/C, if only because the latter is easier to understand at a glance.
Chord names are primarily a shorthand and are not expected to describe function and context in the way a Roman numeral analysis would. So at that level C9sus4 would be equally correct, except to the degree that sus4 and 11 suggest a different placement of that pitch: sus4 would be placed below the seventh; 11 would be placed above.