(Bloomberg) -- For more than two decades, US money managers have looked on enviously as Vanguard Group reaped the benefits of a unique structure that grafted the advantages of an ETF onto its biggest mutual funds. The design, protected by patent, saved its investors billions of dollars and helped the Jack Bogle-founded firm grow into an $11 trillion giant.Now, in what could be the most consequential shift in the American investment industry in years, Vanguard is finally set to lose that competitive edge.Doz ...