Several years ago, I worked at a company called Motif Investing that was conceptually similar this. It was marketed more as a "build your own ETF" kind of thing. You could assemble and weight up to 30 stocks in a "Motif" and manage it over time. We had some of the features you mention as well. I was happy with the product and enjoyed working their, but the business never really took off. I wish you the best in developing your company!