- it should have the character of the most common used features in the worlds languages (not just romance and germanic) - that's why it is called : "VSE-SVETOVIJ JAZIK".
And, of course, it should have vocabulary based on many languages (not just romance and germanic).
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I understand your point of view, you are right.
But it doesn't mean that if such language will be created (or there is already one) it will have success:
- this language will be hard to learn for EVERYONE, not much easier than to learn Chinese for Europeans or Ugric for Africans.
- this language will not be understandable without hard learning.
So, hypotetically, if we have a universal language, it is compulsory for everyone to learn it well. But practically the same if we all will learn Esperanto, Ido, LDP or whatever, it will be not a bit easier for Africans, Chinese and Papua, but only it will be easier for Europeans.
In other words. Imagine that a Chinese or an African is choosing what is easier for him, to learn Esperanto or hypotetical Universal Language? No difference! Even provided a small amount of their native words constructions is used in the Universal Language, it doesn't make it easy.