Shenzhen is poised to get a big boost to its aviation hub ambitions, as China’s industry regulator considers a relaxation of rules that previously sought to concentrate most of the country’s intercontinental air routes to Shanghai, Beijing and Guangzhou.The proposed rule change comes as the southern tech hub breaks ground on a massive expansion of its airport, with the prospect of adding more lucrative services to the US and Europe and intensifying competition with Hong Kong.According to a new...