Late last year, when Indonesia’s biggest property developer was sinking under debt, it was crunch time for the Lippo Group’s Riady family.At a meeting to discuss rescue options, tycoon Mochtar Riady, 90, the founder of the group, turned to his young grandson for help. Reluctant at first, John Riady – a Wharton School graduate – said he eventually agreed to run the troubled flagship PT Lippo Karawaci. His salvage plan included a US$788 million rights issue in July, sale of assets and a debt…