Mercedes-Benz is working on a redesign for its GLS (formerly the GL-Class), and this time around there will be an ultra-luxurious Mercedes-Maybach model to challenge the Bentley Bentayga, Rolls-Royce Cullinan and potentially something from Aston Martin’s rived Lagonda brand. Talk of the Maybach GLS dates back to 2014, and now the first prototypes…