Hi Joey,
Thanks a lot you for your idea. We've recently released reactive web apps, a new generation of web applications that brings several cool features from mobile (and some improvements). Regarding JavaScript you will be happy to know that you'll be able to use the JavaScript node and pass parameters as you are describing. There is also some auto-complete, but it's rudimentary (CTRL + Space), there is another idea to improve that and I hope we can pick that one up.
In these new reactive apps you also need to write a lot less JavaScript, as client actions will automatically compile to it (and are easier to read and change).
As for using (or abusing) the JavaScript node, my recommendation would be to try to centralize its usage as much as possible in reusable libraries, so you don't have high code scattered all over you apps. This will make your app a lot easier to maintain.
Thanks again for your idea,
Tiago Simões