since ECMAScript 6 (the next version of JavaScript) is going to have classes I feel like the need for MooTools Class is dwindling. More importantly, with projects such as
http://github.com/facebook/jstransform you can use classes from ES6 in JavaScript today by transforming your code to ES3/5 - no hacks or performance bottlenecks - just JavaScript. Would anyone be interested in working on a transformer that takes a file and converts all MooTools Classes to an ES6 class so that code can be used with jstransform?
https://github.com/benjamn/recast was specifically invented to do this kind of work. I'd be willing to provide help, guidance and a huge open source repo with MooTools Classes, so if you are interested in taking on something big, let me know :)