Users stay on a website for more than 800ms.

Wouldn't it be more cost effective (rather than convert/port a whole site to a new js lib) to rewrite your page init JavaScript so it does not require a js lib at all (0ms)? Jquery would be async loaded by the time the user executes actions/buttons; if it had not loaded yet you wait, or show a loading icon, etc.

This porting/optimization adds no value to your users 6 months from now who are running a quad core nexus-razr-droid's browser that loads jquery in 300ms.