I'd love to have a streamlined but otherwise version of JQuery which I can serve to known modern web browsers. And serve the 'full' version to non-modern browsers.
Sounds like Zepto is pretty close to what you're looking for: http://zeptojs.com/. Otherwise, jQuery 2.x is just jQuery without support for IE 6, 7 and 8. I'm not sure what kind of performance improvements it offers, but it shaves off a few kb.
