Could you get a grant or two?
Re:open-access? Perhaps. I should note that this area is not my expertise. However, what to do when the grant runs out?
Even so most of our revenue comes from the subscription. A grant may pay for hosting, but what about the time of the developers. Or those working on the publication side. We are already on a near skeleton crew. Especially compared to what we had here in the 1940-80s.
Well, you get another. Lots of non-profits run only on grants.
Have you thought about applying for EU grants? Open Access is one of the goals on Horizon 2020, the €80B EU program[1], but even after that there's no shortage of EU cash being dumped on anything even barely related to "innovation".
[1] https://ec.europa.eu/programmes/horizon2020/sites/horizon202...