Brass is fairly elastic... would steel or SS cases be reloadable? I don't see much point if you only get to use them one time, and I don't hear about anyone reloading commercial steel cases.
It all depends on alloy. 300 series SS is very soft and elastic. 360 Brass (machining grade) is very brittle. Steels are very vast in the alloys with low carbon steels generaly not brittle. Boring berden primed brass cases would probably be the safest or at least most predicatable way to go.
Concentrated power is not rendered harmless by the good intentions of those who create it.