For nearly a decade, the Jacob Riis Bathhouse in the Rockaways has been promised a makeover. This summer was supposed to be when a semi-private beach club finally opened inside the 1930s Art Deco building, including a pool and lounge for paying members. There’s a $750 joining fee, and a standard annual membership will run you $1,500 if you’re under 30 or $2,000 for everyone else. Some of the concessions — slated to include restaurants, bars, a g…