Yes, like the Jaguar XJ13 they put in GT5 that never even raced. Ooh, ooh, or the Nissan R390 Road Car that sits in a museum all day, just like the Toyota TS020 Road Car, Ford GT90 and Renault Espace F1 from GT2 which were some of the most interesting cars to drive. Would you object to them returning? They aren't any more attainable than the X2014.
The list of cars that "have no right to be in the game" (according to certain people) can be stretched to half the car list, yet everybody focuses on the X1 class cars. The fact is, Polyphony can put any car they want in the game and nobody should claim it took resources away from other cars. Unless they were privy to a meeting in which Kaz said "it'll cost us the McLaren P1, but lets do it anyway". As far as we know, it affected nothing.