I think a good first pass would come from studying analytics from npm. What are the most used packages? The most stable? I know lodash makes a lot of sense but there’s also underscore. I think the biggest hurdles are really political over technology as everyone has been so entrenched now that a one-size-fits-all stdlib would be hard. Not impossible, just hard. I do wish someone were working on it and I hate to say it but Google probably has the most skin in the game with v8 and Chrome yet I don’t really trust them not to abandon it. So who else is there? It wouldn’t be a very ‘sexy project’ either but still seems worth it to at least try.
I think it would also make a lot of sense to look at what's in the Python and Ruby standard libraries.