jQuery modal dialog plugin

Question

I'm working on creating a new jQuery modal plugin. I'm pretty good at jQuery but still pretty new to the whole object oriented plug-and-play style of plugins so I used a different plugin I found online and ripped it apart using it as a foundation to build mine. However, I don't feel like I'm taking full advantage of it and not using the whole object-oriented "self" declaration correctly.

Plugin:

(function ($) {
    var DasBtnResponse = {
         Close: "close",
         CloseNegative: "negative-close",
         ClosePositive: "positive-close"
    }
    var methods = {
        init : function (options) {
            var self = this;
            var settings = $.extend({
                    closeable: true,
                    size: "medium",
                }, options || {});
            this.each(function () {
                self.data('plugin', settings);
            });
            methods.setup(this);
            methods.setupButtons(this.find(".DasBtn"));
            return this;
        },
        setup : function (elem) { //Set up the nav DOM elements
            $data = elem.data('plugin');
                 self.wrapper = $("<div />")
                .addClass("DasModalWrapper")
                .click(function(e){
                    if (e.target === this && $data.closeable)
                        $(this).removeClass('open');
                })
                elem.replaceWith(wrapper);
                wrapper.append(elem);
            if ($data.closeable){
                close = $("<div />")
                .addClass("DasClose")
                .html('&#215')
                .click(function(e){
                    wrapper.removeClass('open');
                })
                .prependTo(elem.find('.DasModalHeader'));
            }
        },
        open: function (elem){
            $(elem).parent('.DasModalWrapper').addClass('open');
        },
        setupButtons : function (btns){
            btns.each(function(i, obj) {
                $btn = $(obj);
                switch($btn.data('response')) {
                    case DasBtnResponse.Close:
                        $btn.on("click", function(){alert("close")})
                        break;
                    case DasBtnResponse.CloseNegative:
                        $btn.on("click", function(){alert("negative")})
                        break;
                    case DasBtnResponse.ClosePositive:
                        $btn.on("click", function(){alert("positive")})
                        break;
                    default:
                        break;
                    }
            }); 
        }
    };
    $.fn.initModal = function () {
        methods.init.apply(this, arguments);
    }   
    $.fn.openModal = function () {
        methods.open(this);
    }
})(jQuery);

Init/open example:

$(function(){
    $("#modal").initModal({
      closeable : true
    });
})
$(document).on("click", "#launchModal", function(){
    $("#modal").openModal();
});

Basic (empty) HTML Structure:

<div id = "modal" class="DasModal"> 
    <div class="DasModalHeader"></div>
    <div class="DasModalBody"></div>
    <div class="DasModalFooter">
        <div class="DasBtn btnDefault" data-response="close">Cancel</div>
        <div class="DasBtn btnNegative" data-response="negative-close">No</div>
        <div class="DasBtn btnPositive" data-response="positive-close">Ok</div>
    </div> 
</div>

My main concerns is that I want to avoid directly calling DOM elements/classes as much as possible e.g. this.closest('.wrapper'); and try to use variables instead. Also, there will be many more setting/options and functions this is just the foundation.