The new common language will be more simple and regular than the existing European languages. It will be as simple as Occidental; in fact, it will be Occidental. To an English person, it will seem like simplified English, as a skeptical Cambridge friend of mine told me what Occidental is. To achieve this, it would be necessary to have uniform grammar, pronunciation and more common words. Their separate existence is a myth.
The European languages are members of the same family. Their separate existence is a myth. For science, music, sport, etc. Europe uses the same vocabulary.