UniLang

This is yet another thread on evaluating language proficiency, but in particular, I've been wondering about this: Suppose you're studying an endangered language or some language for which proficency tests are simply unavailable. If you speak some of that language, then how do you evaluate your proficiency in it? Is it possible that the proficiency scale (whether you use the A1-C1/C2 scale or the four-star system) doesn't really work for all (or even most) languages?

Also, is it possible that native speakers of one language may have a greater or smaller vocabulary on average in their language than native speakers of another do in theirs? For example, I've kind of mentioned how in the US, if you want to go to college, you have to take an entrance exam called the SAT, and passing it requires a fairly large English vocabulary. However, I somehow doubt that very many native speakers of Malayalam, for example, have a similarly large Malayalam vocabulary.

As I mentioned in another thread about evaluating proficiency, I used to think that the A1-C2 (or CEFR) system was meant for self-evaluation. Apparently that's not the case, but I still think you could use its guidelines as a way to self-evaluate. I'm sure all the various standards that exist (I know North America uses its own system, and I believe Japan has its own) could be used for self-evaluation.

On first blush I would think any proficiency system could be used with any language, as when they are created, the creators try to make them generic and broad.

As for your last part about vocab size, I think you run into things like how to define a word in one language versus another, what are the core words a native speaker would know, are we looking only at educated, upper-middle class or a "lower" class like blue-collar, or a mix. (Damn, that's a pretty big run-on sentence!) So I'm not sure you could really answer that question.