I maintain that the concept of "sound money" is not a very good one, especially if we talk about a currency aspect of money (as opposed to its store of value one). But that's kinda obvious, provided you have a half-functioning brain and do not obsess with the idea of fiat being inherently evil.
"sound money" usually means either "not prone to sudden appreciation or depreciation" or "commodity-based money". why is that a bad concept? what prevents sound money from being useful as a currency?
paper money backed by gold or silver was used as currency ever since the 13th century, and quite effectively at that.
But I don't know how you are going to replicate in a cryptocurrency the capacity of fiat money to adjust its supply according to the needs of the economy (see the concept of endogenous money to better understand what I'm talking about)
why does the money supply
need to be adjusted at all? you seem to assume keynesian economics is the optimal model but you don't explain why. satoshi designed bitcoin with a hard cap on supply because he obviously believed keynesian economics were the wrong approach to money.