I’m not sure that I’m following completely but we may be muddling things.
Under the current model, if demand for scarce block space increases, so will fees, same as BTC. Certain types of transactions may result in different fee structures such as with ZIP 317, minting and redeeming ZSAs, swaps, storage in legacy pools, etc. There may be revenue generating opportunities for ancillary services. I don’t believe changing the 21M cap is currently under any serious consideration, but that’s up to the community.