People pretty much have and do but the cost spiral out of control and they give up most of the time. I've see a few Renault 5 gtt's start but not finish.. A blue one years ago was in the process of doing a 90% new rebuild but stalled and got sold off, another white one the same sorta time.
At the moment there's a guy doing another white gtt and its on upside down while he's painting the underside and making the underneath good enough to eat your dinner off. It's not 100% oe as there is chrome, but he's buying every nut, bolt, bracket, Clip etc he can. Its a few years in and far from done, but he's dedicated, looks great.