Personally, I think there's two plugins I would really want.
1. Peer-to-peer syncing of notes. I do hope there will be a mobile version someday of your app. Most of my quick jotting of notes happens on mobile and heavy editing happens on traditional laptop/desktop. It would be nice just to scan a QR code to pair up devices and away we go. Optionally a small binary to be the sync server for self host for hub and spoke design. I love Git integration, but we want to take this at a level for those that aren't technically inclined.
2. A robust API for tool integration. Being able to plug in external tools is super helpful for streamlining workflows. In addition I've used it to make accessibility tools integrate for command and control.
I do like the fact that Obsidian has vaults that are essentially separate profiles that have separate vaults location settings and plugins.