Which some home cockpit builders have done. Theres a show on discovery wings with some guy whos built an F-18 with full G-suit simulator that uses air preassure to inflate and deflate the suit when pulling a g-turn. But to get the real effect you really have to be flying.
You can get almost the full effect in a proper commercial flight simulator with a six-axis motion system. I never quite figured out how it's done but you can simulate prolonged braking, even when the full travel on the hydraulic rams is reached. The way it was explained to me is that the system doubles back on itself giving an uninterrupted effect. G effects can be simulated in the same way.
Knowing the lengths some people go to with simpits for the M$ sims, building a functional system to inflate-deflate a G suit (anti-G suit as they were originally called) should not be difficult. The engineering part is basic pneumatics & the necessary valves, plumbing and the suit itself should be readily available on the surplus market. The main difficulty would be in linking this to the sim. I don't know how accurately G is simulated in FS.