I'm not sure what "unearned income" means.

With pegging and gateways there is no need for another non-perishable, mined currency, and any sort of usage tax on a p2p network is unfair and users would rightfully revolt against. So your best hope is that the network effect of people using your software will prevent people from switching to an unencumbered fork. But given that you are providing no direct service to the people using your chain (or it wouldn't be p2p), that is the definition of an unearned rent, and something I would find unethical to take part in.