Class.js

Class.Mutators = {
	Requires: function(items){
		$splat(items).each(function(item){
	        if(!window[item] && Dependencies.Path) {
				//inject file into page
				new Element('script,{
					src: Dependencies.Path + item + '.js',
					type: 'text/javascript'
				});
			}
		});
	}
};

Class.Require Usage

var MyClass = new Class({
	
	options: {
		option1: 1,
		option2: 2
	},
	
	Implements: [Options,Events],
	
	Requires:  [DependencyClass1,DependencyClass2],
	
	initialize: function(options) {
		
	},
	
	//other stuff
	
});