Miners can mine (produce block) and serve user content storage requests.
That's the nodes' job. Running a full node serves the network in two essential ways: It helps it bandwidth-wise, and it insures the presence of the chain in more places. Miners can right as well run a full node, providing extra storage, but their job is to provide computational power.
The Bitcoin full node is hosting the blockchain data (transactions data).
In the EcoPoW design, the miner contributes the computation for PoW consensus, and some disk space for USER's files storage.
Remember it is a blockchain with file storage, something like Filecoin.
However, if the miners are keeping the content for the users, they will receive the payment for storage resource every week.
I think you've confused the purpose of running a full node yourself, and avoid trusting a third party for doing it for you. There's already an incentive on running a full node, that is privacy and security. There's no need to essentially tax the users who don't want to run a full node, which is what you do if you reward those who do run one.
I'm not talking about the full node or even Bitcoin. Dont limit your imagination.
I believe the future blockchain needs sharding (maybe not ETH sharding).
And we're not tax the user. It is the real the storage demand.