I'm a big fan of everything 'VoiceMeeter' and I've got to say, this is right on the mark. It's very simple and barebones, but I can't really think of any features to stack ontop of what's being offered here (direct connectivity).
I'd like to, however, add that I ran into an issue where all of my VoiceMeeter-sources in OBS stopped working. In their source properties they just 'existed', and referred to nothing (as if the plugin wasn't even installed). I have no clue where to even begin recreating the scenario to give you a more accurate description of what the problem really was. I was messing around just about everywhere in OBS at that time. Just a quick OBS restart solved the issue. Just thought I'd let you know.
Anyways, this one is definetly a keeper for me!
TLDR; Make sure the application is running before you start OBS. And I'm crossing fingers they'll have implemented their api fully soon.