By Victoria Waldersee and Ilona Wissenbach BERLIN (Reuters) -Mercedes-Benz expects to have factories producing exclusively electric vehicles (EVs) by the second half of the decade but will steer clear of building EV-only plants, instead keeping production lines flexible in line with market demand. The carmaker foresees some of its production lines within factories switching fully to electric even sooner, production chief Joerg Burzer said in an interview with Reuters. “Building a whole new battery-electric vehicle factory takes time. We have taken another approach,” Burzer said. “We will certa…