Love the idea of custom indices. I happen to know a bit about this question, since I developed an index myself: https://www.mahaadvisors.com/index

I'd start by writing up some sort of methodology behind the index so people can see how it is calculated. For instance, it sounds like it is pure market cap weighted, but the ranking of coins below the chart is not (a few notable outliers are Binance Coin and Cosmos).

I'd also recommend adding some smoothing to the larger time intervals of the graph, since displaying each data point as is causes performance issues and can make it difficult to read, since each individual point is so large.

Happy to talk further, this is an area I've been working on for a while.