Easily Modify genesis theme framework classes on the fly using genesis_attr();

actual-filtering-function.php

<?php

/**
 * Adds Filters Automatically from Array Keys
 */
add_action('genesis_meta', 'bw_add_array_filters_genesis_attr');
function bw_add_array_filters_genesis_attr()
{
    $filters = bw_merge_genesis_attr_classes();
    foreach(array_keys($filters) as $context) {
        $context = "genesis_attr_$context";
        add_filter($context, 'bw_add_markup_sanitize_classes', 10, 2);
    }
}

/**
 * Clean classes output
 */
function bw_add_markup_sanitize_classes($attr, $context)
{
    $classes = array();
    if (has_filter('bw_clean_classes_output')) {
        $classes = apply_filters('bw_clean_classes_output', $classes, $context, $attr);
    }
    $value = isset($classes[$context]) ? $classes[$context] : array();
    if (is_array($value)) {
        $classes_array = $value;
    }
    else {
        $classes_array = explode(' ', (string)$value);
    }
    $classes_array = array_map('sanitize_html_class', $classes_array);
    $attr['class'].= ' ' . implode(' ', $classes_array);
    return $attr;
}

/**
 * Default array of classes to add
 */
function bw_merge_genesis_attr_classes()
{
    $classes = array(
            'content-sidebar-wrap'      => 'row',
            'content'                   => 'col-xs-12 col-sm-8 col-lg-7 col-lg-offset-1',
            'sidebar-primary'           => 'hidden-xs col-sm-4 col-lg-3',
            'archive-pagination'        => 'clearfix',
            'entry-content'             => 'clearfix',
            'entry-pagination'          => 'clearfix',
            'sidebar-secondary'         => '',
    );
    if (has_filter('bw_add_classes')) {
        $classes = apply_filters('bw_add_classes', $classes);
    }
    return $classes;
}


/**
 * Adds classes array to bsg_add_markup_class() for cleaning
 */
add_filter('bw_clean_classes_output', 'bw_modify_classes_based_on_extras', 10, 3);
function bw_modify_classes_based_on_extras($classes, $context, $attr)
{
    $classes = bw_merge_genesis_attr_classes($classes);
    return $classes;
}

example-add-new-classes.php

<?php
/**
* Template Name: New Classes Template
* Description: Example modifying page classes on the fly
*/

//* Custom classes on the fly like in a page template
add_action('genesis_meta', function(){
    add_filter('bw_add_classes', 'bw_custom_example');
});

function bw_custom_example($classes) {
    $new_classes = array( 
        'nav-secondary'  => 'navbar navbar-inverse navbar-static-top nav-blue',
        'entry'          => 'panel panel-default',
    );
    return wp_parse_args($new_classes, $classes);
}

genesis();

layouts.php

<?php
/**
 * Modify Layouts
 */
add_filter('bw_clean_classes_output', 'bw_modify_classes_based_on_template', 11, 3);
function bw_modify_classes_based_on_template( $classes, $context, $attr ) {
    $classes = bw_layout_options_modify_classes_to_add( $classes );
    return $classes;
}

function bw_layout_options_modify_classes_to_add($classes) {
    $layout = genesis_site_layout();
    // full-width-content
    if ( 'full-width-content' === $layout ) {
        $classes['content'] = 'col-sm-12';
    }
    // sidebar-content
    if ( 'sidebar-content' === $layout ) {
        $classes['content'] = 'col-sm-12 col-md-8 col-lg-9 col-md-push-4 col-lg-push-3';
        $classes['sidebar-primary'] = 'hidden-xs hidden-sm col-md-4 col-lg-3 col-md-pull-8 col-lg-pull-9';
    }
    // content-sidebar-sidebar
    if ( 'content-sidebar-sidebar' === $layout ) {
        $classes['content'] = 'col-sm-6';
        $classes['sidebar-primary'] = 'col-sm-3';
        $classes['sidebar-secondary'] = 'col-sm-3';
    }
    // sidebar-sidebar-content
    if ( 'sidebar-sidebar-content' === $layout ) {
        $classes['content'] = 'col-sm-6 col-sm-push-6';
        $classes['sidebar-primary'] = 'col-sm-3 col-sm-pull-3';
        $classes['sidebar-secondary'] = 'col-sm-3 col-sm-pull-9';
    }
    // sidebar-content-sidebar
    if ( 'sidebar-content-sidebar' === $layout ) {
        $classes['content'] = 'col-sm-6 col-sm-push-3';
        $classes['sidebar-primary'] = 'col-sm-3 col-sm-push-3';
        $classes['sidebar-secondary'] = 'col-sm-3 col-sm-pull-9';
    }
    return $classes;
}


/* Move sidebar wrap */
remove_action( 'genesis_after_content_sidebar_wrap', 'genesis_get_sidebar_alt' );
add_action(    'genesis_after_content', 'genesis_get_sidebar_alt' );

Use this debug function to print all known page attributes

https://gist.github.com/bryanwillis/16f1755f07e507f2b3b6