most of them not holding their value
I agree with your assessment on previous Brooklin models not holding their value. These non-essential white metal models have always been expensive, and although I don't collect for investment, it is comforting to know that if I spend a significant amount of money on a non-essential item, it will at least hold its value.
That said, Brooklin has slowly evolved, but evolved nonetheless, and has come a long way since the release of the 1958 Pontiac Bonneville convertible.
Looking back at their models, I see significant improvements mostly starting in 2009, and then again in 2015.
Brooklin has been late to the game adding resin headlights, chrome trim and outside door mirrors, when all the other model crafters have been adding these things for years, but they have caught up with these new NBC models, and if I had to guess, I would say you will be seeing these extras on all their models soon.
If these NBC models, limited to 50 each, don't become sought after collector models, I don't know what will.