> is there a historical business model, or models, that we could mimic?

Good question! Usenet and IRC were often hosted by ISPs, which users paid for indirectly with their internet subscriptions. People also paid for access to Usenet. DejaNews was a popular archive/provider service before it was bought by Google. On IRC people pay for service providers to keep them constantly connected (bouncers) and provide vanity DNS names. Also, people pay to run bots like Eggdrop to manage/moderate their channels.

For email and HTTP there are the obvious hosting and other service providers, but I suppose the biggest value they support is the things built on top of them, which is maybe fitting for a general-purpose protocol.