I enjoyed your essay Jens,
I also feel strongly that what you propose is something we must do, in order to preserve the continuity of human knowledge - crisis or no. Moreover; I think that all steps taken in that direction are needed and bound to be helpful in the long run. I think both a grass-roots effort and a government or corporate funded one are in order. You have my support for your project, and I can offer insights about how certain technical functionality might be implemented, but for now a comment about robustness.
Any attempt to make a truly robust repository faces the kind of human bias problem Phil Gibbs talks about in his current essay. You probably wouldn't want the same people running arXiv dot org in charge of your repository, because some essential information would be submitted but left out. And if you had an inclusive model, as with viXra dot org, some people might complain that the standards of those maintaining the repository were not sufficiently high. So a challenge would be to assure that there would be adequate peer-review and fact checking, without bias. I'll have more to say on this later.
Good Luck!
Jonathan