On the whole, I think you not to work on keeping it simple.

• I would not write my own cross-browser event handling function if I use jQuery, I would leverage what jQuery provides.

• This:

    /* standard JS */
    function InitStandard(jQuery) {
        //get device information
        this.device = new Device();
  
        // initialise jQuery, if device is capable
        if (this.device.quality === 1) {
            this.jqueryPlugins = new InitJquery(jQuery);
        }
    }
  
    /* initialise standard JS on load and pass in the jQuery object */
    (function init(jQuery) {
        var js = new InitStandard(jQuery);
    }(jQuery));
  

  could be

    (function InitStandard(jQuery) {
        //get device information
        this.device = new Device();
  
        // initialise jQuery, if device is capable
        if (this.device.quality === 1) {
            this.jqueryPlugins = new InitJquery(jQuery);
        }
    }(jQuery));
  

  Because you are not using var js anywhere.
  Also, 1 should be assigned to a properly named constant like ADVANCED_DEVICE

• addEvent(window, 'load', init); could be $( init )

On the whole, I think you need to work on keeping it simple.

• I would not write my own cross-browser event handling function if I use jQuery, I would leverage what jQuery provides.

• This:

    /* standard JS */
    function InitStandard(jQuery) {
        //get device information
        this.device = new Device();
  
        // initialise jQuery, if device is capable
        if (this.device.quality === 1) {
            this.jqueryPlugins = new InitJquery(jQuery);
        }
    }
  
    /* initialise standard JS on load and pass in the jQuery object */
    (function init(jQuery) {
        var js = new InitStandard(jQuery);
    }(jQuery));
  

  could be

    (function InitStandard(jQuery) {
        //get device information
        this.device = new Device();
  
        // initialise jQuery, if device is capable
        if (this.device.quality === 1) {
            this.jqueryPlugins = new InitJquery(jQuery);
        }
    }(jQuery));
  

  Because you are not using var js anywhere.
  Also, 1 should be assigned to a properly named constant like ADVANCED_DEVICE

• addEvent(window, 'load', init); could be $( init )