ActivityPub I believe gives us enough metadata to have enough of a social site. Although it all started from GNUSocial (or whatever it was called) and similar open sourced twitter-like platforms, it doesn't necessarily mean we should be restricted to "micro" blogging by those platforms (besides, sharing pictures, and such is somewhat still valid "micro" blogging just look at Tumblr). If the limits are too much you could still at the very least send over a summary between hubs and if the person wants more info they can visit the originating site for the whole post.
I think the path forward is to use open and standardized formats / protocols. We have the technology... There's a couple of implementations for ActivityPub/ActivityStreams already[2], you could either join one and contribute or just start one yourself if none are in the language / license you prefer.
[0]: https://www.w3.org/TR/2018/REC-activitypub-20180123/
[1]: https://www.w3.org/TR/activitystreams-core/
[2]: https://github.com/w3c/activitystreams/tree/master/implement...