Almost everything humans do is a gimmick. Eating anything other than nutrient slop is a gimmick. Gimmicks make life interesting.

Huh? This paper is about the economics or gain from adding solar powers to vehicles hence my statement that it’s a gimmick and it adds complexity (cost) for a gain that is not beneficial. Now if we were talking about marketing the vehicle, sure it perhaps drives a fun idea for buyers.

From an economic standpoint solar panels on vehicles are a gimmick.

One thing the paper does is introduce a mathematical model that allows us to decide when it's a gimmick and when it actually becomes useful. As PV panels get more efficient and lighter, there is a point it'll start to make sense despite conversion losses. It's very unlikely to make much sense in Sweden (or even in Ireland, where I live), but different locations, with different infrastructure and, most important, solar exposure, will drive different economics.