Being able to install a block from within the editor sounds like a good idea to me. I find it similar to installing an extension in VS Code: while programming, if I find I need a certain functionality, the UI allows me to quickly install an extension, which will be enabled instantly, without having to restart the application. Programming like this is such a breeze. If Gutenberg could achieve something similar, so that the user could install a required functionality while editing the post, would be pretty helpful. (It’s one of those things that you don’t pay much attention to, but once you have it, you can’t do without it.)

However, I do agree that this can lead to bloat, allowing users to install more blocks than are required. So the UI should make it easy to install blocks, but not so easy as to be overused, and always making sure the user knows what he/she is doing. And not all users should have access to this functionality, so I guess a capability “can_install_blocks_from_editor” would make the site admins be able to sleep at night.

My vote is for it, but only if it is done properly.