A few years ago GlobaLeaks published their grant application and progress report. I’m unable to find them easily but they are surely archived somewhere and would be a great source of inspiration.
OT: I see you consistently not naming what for most developers will be the key benefit of federation (it relates to “Open Society” of OTF), namely that it will unite the fragmented landscape of self-hosted forges (that are now very hard to find, and where each time one should go through the friction of creating yet another account).