Oh! I never thought about the "reprise on a car" as a way to show parallels, but it brings up an interesting point in the lines they sing there:
With Sadia they're reprising the violent nihilism song, about doing stuff (violence) today bc you need to live life to the fullest as there is no tomorrow. The car there is a symbol of things falling apart (literally being dismantled and tagged as they're using it)
With Cristal, and despite the slight disconnect I always feel from the coup d'éclat/plus rien à perdre/Monopolis lyrics sequence, at the moment of Monopolis they're singing about a future together, and seem to be using the car as a getaway to that future (finally leaving the holding pattern of the hangar where you're safe but nothing happens, for the first time as far as we know, to go meet whatever is in the cards for them because they'll face it together.)
As for the bit of Sadia's silver dress that uses bits of the Cristal Monopolis dress fabric in silver, @braimee pointed it out to me recently and I had literally never paid attention lol To me it seems like too small a detail to be of real significance -- if the actual silhouette of the dress were similar, then sure, but it's just a little bit of the same fabric being used in a dress whose pattern is 100% Sadia's leather dress, made out of various sparkly fabrics instead.
For me, if it has significance at all it's a way to show that Sadia's is "back to the upper class" roots, using the kind of rich, textured, sparkly fabrics that all the upper society women use (whether it be Cristal or Stella), while Cristal has swapped her own sparkly dress for a somewhat drabber Etoile Noire ensemble (with added flair of course :p)