|I think it depends on the film. As you point out, Warhol and FFH use the source material as a departure point. Mabye the Richard Gere Breathless would fall under the moniker of re-make? (It's been 20+ years since I last saw Herzog's Nosferatu but I remember it as being pretty faithfull to the original, just four times as long)
I like the term "literary stratagy" for these films but in the case of FFH I prefer the label high-concept as I think of Haynes as the gay Oliver Stone.