MUMBAI, Nov 15 (Reuters Breakingviews) - Buying bits of a bank is complex at the best of times. When it involves one of the planet’s most highly charged territorial disputes, it takes a truly daring chief executive to take the plunge. Piyush Gupta of $65 billion Singaporean lender DBS Group (DBSM.SI) appears to be that CEO, whether he thinks of himself that way or not. The 62-year-old former Citigroup (C.N) banker has led what’s now Singapore’s largest bank by assets since 2009. During that time, DBS’ total return to shareholders is more than 340%, around seven times the level of...