* Germany opposed to common budget (Adds comment from Soros spokesman): FRANKFURT (Reuters) - Billionaire investor and activist George Soros has met a European Central Bank director to argue for closer euro zone integration, prompting criticism from some EU lawmakers who fear he is exerting undue influence on a sensitive political issue. The Hungarian-born financier is a veteran advocate of European unity whose championing of liberal causes over decades has earned him many enemies, including Hungary’s nationalist Prime Minister Viktor Orban and some Brexit supporters.