The description on that wiki page describes the current slider
implementation. As mentioned in the
GSoC wiki
, we want to rewrite this widget, including a redesign of the API.
Starting with a prototype seems like a good idea to me. You could also
draft up a new API based on the existing spec, the implementation in
jQuery Mobile and the suggestions on the ideas list (multiple widgets
instead of just one).
To get started with contributing to jQuery UI, you could look into
fixing one of the
existing slider bugs.
We can also discuss this on IRC, #jqueryui-dev on Freenode.