This is the question I have too. The ability to create a "custom" ETF is highly desirable to me. I don't want to trade individual stocks, but instead would rather input some weightings on top of existing indexes (i.e buy less of stock A, more of stock B, etc.). However, my understanding of ETFs is that they are able to rebalance through "in-kind" creation/redemption in order to avoid creating a taxable event. I'm not sure how this is possible to scale to a custom one-off fund...