Nice writeup. While I don't follow Stablecoins all that closely it definitely is interesting to see a comprehensive list of approaches at controlling volatility.
I'm not quite convinced that stability can be reliably achieved within tolerance levels that are acceptable for the general populace (say, < 5%) but they do give an opportunity to look at market forces in wholly new ways.
I don't really find the reason how stable coins are beneficial in the market? Can someone quote and answer this question? but I guess this stable coins will going to help large business investors who entered the market.
Medium of exchange + store of value.
Without a mechanism to reduce volatility, an unstable cryptocurrency will not be able to serve that purpose.