@extropic You wish number 3 is granted :-)
What is left to be done by You:
1. Create accounts on the servers, from which you want to "pull timelines” and subscribe to that timelines.
2. Or you can remotely subscribe to any remote User's feeds via GNU Social web interface, and then have all these ”User timelines” arrived to one your account.
In practice, I combine both of these approaches. Please see attached my list of Home timelines for several accounts. On that screenshot you can see when and how many messages were downloaded via each account.
Approach no.1 allows you, using ”Search” timeline, pull something interesting from the Public timeline of each GNU Social server also (and sync this Search timeline automatically!)
I hope that GNU Social developers will fix a problem in the Server side code, which causes unnecessary traffic of such Search Timelines (I reported that issue two months ago already https://git.gnu.io/gnu/gnu-social/issues/206 @mmn ) https://loadaverage.org/attachment/3220490