Ability to communicate freely and even to think fluently in foreign language does not provide guarantee that you will be able to transfer information on high quality level from foreign language to local language. The word “quality” does not mean simply transfer of meaning, but rather to keep the language beauty, as far as exactly in the ability to transfer the essence beautifully and accurately lies the skills of a translator. Each language has its own unique peculiarities: grammar turns and structures, peculiarities of sentences construction, idioms etc. This is at least not professional to ignore all of the mentioned factors and to limit oneself to “transfer of sense”.
Therefore, if you “entrust” the translation functions to the employee with “advanced” level, you will face the risk of dilettantish translation, as regarding documentation, as well as during negotiations. This will be especially important with respect to the negotiations, as far as interpreter is the only link between you and your partners. And successful completion of a business meeting will depend on the professionalism of your interpreter.
Therefore, the translator is a profession. And like any other profession it requires skills, knowledge, experience and talent at the end.