We need:

• Know whole js file to be included for one survey before survey start : then move js inclusion elsewhere
• A good versioning of survey (change an question advanced parameters can add js or css)
• A good versionning of template.js and template.css

Maybe an option in survey 'use minify' can be great too.
I think admin user can deactivate minify and force calculation of minified file.

We need to to create the file and call it if exist, else do it : caching issue.

There are a lot of minify/js minify/css PHP script can be taken.