If I’m correct, the current iOS app is only able to use PNG files so one should always need to convert first.
Just creating a set in the icons/classic would do for now, but it would indeed be awesome if you could configure UI’s to use a different icon set.
Anyone up to the challenge?
BTW, I have already started developing a smart python script to generate my own set as a proof of concept. When it is working I will upload it to a repo for sharing.