I understand the idea behind costume threads and I think it works well.
That said, I would suggest a slight tweak. Instead of having a single thread per hero, it would be nice if the thread was global (works for any hero, but all heroes cost x thread). As it stands, everybody will end up having the same costumes at the same time because there isn’t a choice. If it was a shared thread, we would get different choices as players choose their favorite hero / costume and it will be more meaningful.
Food for thought.