Sotheby's potion belt and bag isn't just adorned with gold to show how absurdly rich she is, it has a practical use as well. Pure gold is a very chemically unreactive substance, and considering how many poisonous, acidic, and highly reactive alchemical substances she deals with on a daily basis, it makes sense she'll use a material that won't easily melt off or get damaged from repeated exposure.
Why does Lilya ride her fighter plane around like a broom? At first it seems like a way to add witch-like elements to the Arcanist but upon further digging through, it turns out that it's a reference to the first ever Women's Aviation regiment during the Soviet era of WWII. Their name? Night Witches
