> CVC roots (20*5*20
> makes 2,000 roots or less, which is clearly insufficient).
Mandarin Chinese manages with a CV syllable structure, 24 consonants, and 21
vowels, making a possible total of 501 syllables - not all of which actually
occur! So 2,000 does not seem so impossible by contrast.
Mandarin copes, of course, through tones (4 plus neutral) and through a
large number of bisyllabic words - e.g. the form that gave "look-see" in
English. So a language with "2,000 roots or less" could certainly devise
strategies for unambiguous communication.
We already know that accent helped to differentiate forms in PIE. A "2,000
root or less" language could also easily have had accents, tones or
suprasegmental elements that don't show up in the brute arithmetic of
consonants and vowels.
So your statement that it is "clearly insufficient" is not necessarily
correct.
Peter