I'm still uncertain which option to chose tbh.
Stainless could be pretty nice in terms of aesthetics.
However even stainless steel is not fully rust proof depending on the kind of steel, finish etc.
I've seen surface rust on stainless before so I'm slightly scared to vote for raw stainless.
In adition stainless is still less heavy then brass.
Brass is actually really nice but wouldn't make the carbon edition stand out enough compared to original.
In my opinion the only real solution would be to go for nickel plated brass or something similar.
Nickel plating was actually considered a while ago, and this way there wouldn't be any downsides.
You would get color neutral stainless like asthetics, no risk of rust, same wait as brass and an overall very premium feel.
Even if it increases carbon prices it would honestly feel like the best choice to me, since it's supposed to be the premium edition.