I try to extend standard magento javascript configuration but I just get nothing.

I'm following this:
http://devdocs.magento.com/guides/v2.1/javascript-dev-guide/javascript/custom_js.html
and this:
http://devdocs.magento.com/guides/v2.1/javascript-dev-guide/widgets/widget_calendar.html

To do so in my theme I placed a requirejs-config.js like so:

var config = {
    map: {
        '*' : {
            'myScript1' : 'js/my_script_1',
            'mage/calendar' : 'js/calendar',
            'mage/tabs' : 'js/tabs'
        }
    }
};

my_script_1.js looks roughly like so:

define(['jquery','mage/tabs', 'domReady!'], function ($) {
    $.fn.myFunction = function () {
        // some code ...
    }
});

I can then access that function in my product_page.phtml like so:

<script>// <![CDATA[
    require([
        'jquery',
        'scrollToTarget',
        'domReady!'
    ], function ($) {
        $('.foo').myFunction();
    });
    // ]]>
</script>

This works well.
Now I want to do roughly the same in the other two files. But here I want to extend existing functionality.

Here is the js/calendar.js:

define([
    'jquery',
    'jquery/ui',
    'mage/calendar'
], function($){

    $.widget('<vendor>.calendar', $.mage.calendar, {
        calendarConfig: {
            showWeek: false
        }
    });

    return $.<vendor>.calendar;
});

Here is the js/tabs.js:

define([
    'jquery',
    'jquery/ui',
    'mage/tabs'
], function($){

    $.widget('<vendor>.tabs', $.mage.calendar, {
        /**
         * Instantiate collapsible
         * @param element
         * @param index
         * @param active
         * @param disabled
         * @private
         */
        _instantiateCollapsible: function (element, index, active, disabled)   {
          console.log('fooooo');
        },

        _myFunction123: function (foo) {
            return foo;
        }
    });

    return $.<vendor>.tabs;
});

But both extensions (calendar and tabs) don't work. The calendar still shows the weeks and that console.log() in tabs.js is never triggered.

What am I doing wrong here? How do I have to extend this?

EDIT:

So at least the calendar config can be changed like this.
Overwrite app/design/frontend/<vendor>/<theme>/Magento_Theme/templates/js/calendar.phtml
with the original files from Magento itself and change options there.
But this does not reflect the way described in the docs.