I'm wondering if someone has tried already to port jQueryMobile on top of Zepto.js (http://zeptojs.com/) instead of the required jQuery?
The main feature of Zepto.js over jQuery is its file size of ~10kb (minified, not gzipped) instead of jQuery's ~80kb. If you were to replace jQuery wuth Zepto.js then you'd still have to include jQuery mobile, which weighs in about 95kb (JS & CSS).
You'd save about 1/3rd of the download weight (not including HTML, images and other JS), making making a port of jQuery Mobile to Zepto.js unlikely to be worth the time.
Zepto.js currently also only supports WebKit browsers, meaning you'd be loosing support of Firefox Mobile and IE7&9 Mobile too.