I want a single feed that I can customize and preferably weight based on how important I think something is.
The perfect solution would support Lemmy, RSS, Mastodon and maybe even Bluesky. And would allow me to increase the visibility of certain content. For instance a specific RSS feed
You have Mastodon and Lemmy covered with a piefed, friendica or mbin instance.
You can follow RSS feeds from a (microblogging) fediverse account using https://rss-parrot.net/ - so that covers that part. Apparently Bluesky provides RSS feeds, so this also works for Bluesky, although I have not tried that yet because I’m not aware of anyone posting only on Bluesky that I would want to follow.