The thing that annoys me is that there is no propper way (at least to my knowledge) to run multiple linked fedi accounts. I have a selfhosted misskey instance, but then should I also run pixelfed? Or should I just use the singular instance?
It would inherently require trust, so the only way it would scale beyond self-hosters controlling their own domain would be co-hosted alongside some SSO-unified fedi services (or if S2S delegation becomes an adopted thing).
(If you run with this idea, consider AGPL for all parts :))