Up until now, no-one in DeFi has figured out how to provide a risk-free rate on a stablecoin. You cannot simply just replace proof-of-stake with proof-of-stablecoin-deposit due to security implications.
However, if a solution existed, it would generate huge demand and liquidity for the stablecoin, as nodes will need to hold stablecoin in order to accrue revenue.
I am the co-founder of a startup Cambridge Cryptographic, and we have achieved a solution which we outline here:
Would be great to hear what people think of this.