i've read Human Action, twice. and his key point is you don't need increased supply, only smaller denominations. if the economy grows, the prices of everything decrease, and this tends towards needing smaller denominations.

we already literally saw this deflation with technology for the last 100 years. nobody died from it lol.

so there is also no need to expand the money supply. based on how Mises describes it, if a money supply doesn't increase (it's a mind experiment) then if prices don't decrease it means there is either a decline in progress or a decline in aggregate production.

prices of stuff, all things being equal, meet at the middle point between supply and demand. if demand goes up, price goes up. if supply goes down, price goes up. if cost of production goes down, that tends to mean supply goes up and price goes down (jevon's paradox).