Hi, I am a developer with backend/API focus with 10+ yr experience. My current main project is a cryptocurrency, a custom block-lattice based coin with fast transactions and no fees. I am involved with the core node programming, wallets, and webservice APIs as well. I am familiar with some payment integration APIs (e.g. for bitcoin payment processing), and several crypto exchanges.
As I understand you need hindsight analysis ('what would have happened') of selected crypto portfolios over a given past period, either individual cryptos or a mixture. Porfolios can be static mixture, or dynamic, e.g. based on market share. Eventual exchange fees must be estimated and considered (configured rates). UI presentation does not need to be very fancy (not a product to sell), but practical (with handy functions such as saving configuration, portfolios, results). Response time is not prime concern, it is more important to be able to visualize results, and be able to easily compare and find analysis results. Graphical visualization is a must. This could be done by a simple web-based UI and simple backend.
I wonder how much infrastructure is available (e.g. for hosting the backend and the app), and how strict are the technical requirements. Also, if it would be OK with you to develop this as an open source software.