As ffrank said your salesman is being a bit naughty. No options will get you your money back but nothing really will make it less desirable. Going to be plenty of vanilla spec gti/gtds on the market as they are well specced as standard.
The GTI and GTD have good standard specification anyway which was one of the original reasons I readily moved from being a faithful Audi A3 driver so like has been said, the second hand market for MK7 GTI and GTD will be very solid as even the most naive of buyers will get a great car with regards specification.
With regards DCC and some of the other options then I am sure the more discerning buyer will seek out these as additional options but doubt they would be adding any real value it would be
condition and mileage that sets the price.
Thing again it has been said on this forum that you specify options because you want them and not for the resale value.
With regards DCC and having been regularly in a colleagues vanilla GTI I would say there is an obvious improvement in the comfort of the ride, the DCC really does cossett the worst of roads and without any real compromise to the handling. Its a luxury ride.
However, having been in the vanilla GTI, the ride is still decent and more than acceptable as you do feel the ruts to a degree but it does not crash or anything as it rides over them.
Like all options it depends how much you value what it is giving, if comfort is a huge tick, then you have to have DCC, if it is not then you would not really be suffering without either.