Search "Everything"!

Problem: I just signed up to a few instances and noticed that searching for the same keyword yields vastly different results. Which not only makes me wonder: How can I use Mastodon and get the most out of it (aka not miss valuable content). But also: How am I supposed to post something and reach the widest possible audience. It's extremely obscure.
Moreover, it makes choosing the instance overly complicated. Before I signed up I was under the impression that it does not matter that much, because I could still access everything outside the instance through "Federated". As it turns out "federated" = "someone followed by someone from your instance".

The federationBot from mastodon.host adresses exactly this need to see the most possible content. (It doesn't help with posting to the biggest audience, though)

Home, Local, Federated, UNIVERSAL

In my opinion (I've been on mastodon since yesterday... (yes, I'm a tumblr refugee)) it would be very beneficial to have the option to Search "Everything", universally/globally. An "universal timeline" on the other hand would probably be unusable.
This should, of course, respect blocked lists and similar settings from the user and instance (eg. blocking certain tags/words, blacklisted instances, SFW filters etc).

Benefits

• easier to discover interesting people from other instances. (Like, how do I even discover someone who isn't followed by anyone from my instance right now??)
• easier to find content that has no specific "interest" instance right now, or could fit into different instances with overlapping interests. And vice versa less thinking about "now where do I post this?"
• Right now, the logical step is to just join the most popular instance to have access to the widest audience/content. Which somehow opposes the whole idea of "decentralization".
• Consistent search results when using Global/Universal search option.
• Less need for multiple accounts on different instances

Disclaimer

I searched the issues, but couldn't find exactly this feature request. I read about the relays. And some suggestions like "I want to subscribe to a whole instance timeline" which adresses a similar need.
I am aware that the whole system probably does not support access to literally everything.
Also: I do not intent to replace Federated, because it has value in curating and filtering content.