That’s exactly what I aim to solve with rocket:module! Here’s more info in this post.
The basic idea would that you write your library in a normal node type way (f.e. using CommonJS modules) then rocket:module will let you import it from npm into your Meteor project. This is good because then you can do
var something_else = require('other_lib');
instead of
var something_else = Meteor.npmRequire('other_lib');
in your library code, so it’s more portable, and not limited to the Meteor ecosystem.