I guess lemmy doesnt know iti s a one-man instance. and it allows for a consistent source for media (ie your home-lemmy).
I have always thought that it should be a time/size limited local cache, like you are happy to assign 50Gb to local cache of all assets from other instances, and it would keep it to size on a first in first out type of setting. Or, keep remote assets for up to 6 months.
When the cached asset expires, lemmy will then point to the original source.
but, i am not a dev.
Yeah, that sounds like it must sync all subscribed comms to your instance, media and all