Our custom YUI2 makes each page significantly bigger and slower to load, the problem is our current code still relies on YUI2, we need to clean all core JS first and then load YUI2 only when necessary.

The second step is to use official YUI2 loading from YUI3.

the would change public API and some old code that works now would have to be rewritten, so I guess 2.0.x is not an option...