Are you talking about the editor or the runtime? In the editor, generally I don't think you don't need to do anything complicated so such a library isn't so useful. In the runtime, it is a terrible idea to use them for GC reasons. Box2D is horrendous for causing big GC pauses, precisely because it uses b2Vec2. Your proposed solution does not really solve the problem because you still need to have 100% perfect recycling of the objects you pass to those functions, or you create GC problems still. It is very difficult to write code that does this, because you need to invent a clear system of ownership and make sure you get your "free" calls in exactly the right places, which is error-prone. So it really is better just to avoid them completely.
If you really, really need it, you can probably find your own JS math library and integrate it. But you should be extremely careful not to slow down the games using your plugin.