There are two things being discussed here. The first is the original suggestion of the account you'd log into and use as a server for pulling information. The other some have mentioned is the location of communities. They both share similar problems in an overloaded or defunct instance situation, but need different solutions.
For the account I think just one main thing needs developing, and that's the ability to share a profile across different logins. So you can have two or three different logins, but you have the same settings and when people interact with you they see you as the same umbrella/main account. I'm not sure how this could work outside Lemmy, like kbin or even Mastodon without being part of the protocol itself, but maybe that's a long range idea. There's also the problem of name collision since there's enough accounts now that duplication is probably a thing. The choice right now is limited to just making accounts in a few places and see if things are better/same/worse there before you get too invested with customizing your stuff.
For instances - I had seen a suggestion of having a grouping ability between different instances that wanted to share or mirror each others content, basically an automated cross-posting. This would allow multiple instances so if one has some problem, the content still exists. There's lots of caveats with that I'm sure, but one of the laments from many Redditors is the loss of resources, and that really should be a high priority to make sure that content is both preserved and available. For now the best we can do is make communities in a few places and cross-post the more important things so more people read and respond to it.