Blanthos

figured there would be some reason it wouldn't work, although it raises the question then of how compounding nicrosil would work

I'm not sure if this actually works the way I think it does, but basically, you need to be a nicrosil compounder and either a Lightweaver or an Elsecaller (so you can soulcast. Then, what you do is you breath in some Stormlight, store it in a nicrosilmind, compound it, and use that Investiture to soulcast things into nicrosil, which you can then compound, and use the resulting Investiture to soulcast more things into nicrosil, and so on.