For cost reasons, quality, and security, I think it should absolutely rely on open-source pieces (and be an open-source project itself, to allow for public review and efficient feature growth). Whoever (individual, group) assembles said solution should therefore become a de facto contributor to all projects used, if only for the sanity of the arch-project.
The matter of profitability bugs me though, because it should not be for profit but you need full-time devs and actually a whole company to run the project with excellency (it needs to be 'sold' to users, I mean promoted to be known and used, a bit like NGOs, and supported/maintained), so I think opt-in marketing (ads, or taking a cut on peer-to-peer contracts like Spotify I mentioned) could be one way of doing it. Ideally, the corporate structure would be not-for-profit so there's no dividends (people and businesses get value but the actual structure doesn't beyond paying employees and contributions, that should be enough incentive for all actors, B or C or states, to root for its neutral continuation, kinda like DNS or email). The point being that everyone had motives for it to exist but no one would profit directly from it, only through it. It's like the police, or the state itself, or public streets: collectively supported.
The Open Source community needs an open committee founded on promoting projects of this nature. -- [Open committee over closed since such a foundation could easily be corrupted by personal interests]
A notable act would be to join the course of an ongoing project, if one which is flexible enough to build onto exists.