I don't see why a decentralized credit rating system could not exist, as well as a token issued based on said rating.

What real-world problem are you trying to solve? What unmade loan do you want made that a decentralized credit-rating system would make but existing system cannot? What cost or risk do you want to reduce? What screw-up do you want to avoid? You seem to want to build a better unicorn trap.

A central banking issues the monopoly currency (not to be confused with "Monopoly money"!) accepted by the government in payment of taxes and fees. A parochial "dynamic supply" algorithm isn't central banking, as it cannot effectively control the level of money creation by all of the banks in the economy. No crypto system can have the monopoly necessary to support central banking so long as the government's money is around to compete with it.