This idea has been merged into another idea. To comment or vote on this idea, please visit PL-I-381 Global blocks: folders, search, site-scope.
In addition to global blocks, "site-global" blocks would be useful. When you work with multiple sites with different editors global blocks easily gets messy.
Site-global block would be re-usable like global blocks but only visible then you are editing the site the blocks are connected to.