[WP] Merge Multiple Queries / Loops into one

WP_merge_multiple_queries.php

<?php

// Check if values are cached, if not cache them
//delete_transient('home_slider_24h');
if(get_transient('home_slider_24h') === false) {

	// RM Blog (post) query
	$rm_blog_args = array(
		'posts_per_page' => 1,
		'cat' => 10,
		'post_type' => 'post'
	);
	$rm_blog = new WP_Query($rm_blog_args);

	// F&B (post) query
	$fb_args = array(
		'posts_per_page' => 1,
		'cat' => '463, -505',
		'post_type' => 'post'
	);
	$fb = new WP_Query($fb_args);

	// How-To (how-to) query
	$howto_args = array(
		'posts_per_page' => 1,
		'post_type' => 'how-to'
	);
	$howto = new WP_Query($howto_args);

	// Knowledge Base (knowledge-base) query
	$kb_args = array(
		'posts_per_page' => 1,
		'post_type' => 'knowledge-base'
	);
	$kb = new WP_Query($kb_args);
									
	// Final Query
	$final_query = new WP_Query();
	
	// Merging queries
	$final_query->posts = array_merge( $rm_blog->posts, $fb->posts, $howto->posts, $kb->posts );

	// Recount
	$final_query->post_count = count( $final_query->posts );
									
	// Cache Results
	set_transient('home_slider_24h', $final_query, 24 * HOUR_IN_SECONDS );
									
	// Remove duplicate post IDs
	$post_ids = array();
	foreach( $final_query->posts as $item ) {
		$post_ids[] = $item->ID;
	}
	$unique_posts = array_unique($post_ids);

	// Cache Duplicated Posts Results
	//delete_transient('home_slider_duplicated_posts_24h');
	if(get_transient('home_slider_duplicated_posts_24h') === false) {
		set_transient('home_slider_duplicated_posts_24h', $unique_posts, 24 * HOUR_IN_SECONDS );
	}
    
}

// Get cached results
$final_query = get_transient('home_slider_24h');

// Get posts to exclude
$posts_to_exclude = get_transient('home_slider_duplicated_posts_24h');

// Looping
if($final_query->have_posts()) : while ( $final_query->have_posts() ) : $final_query->the_post();

// post layout and output goes here...............

endwhile; endif; wp_reset_query(); wp_reset_postdata();

?>

This code is really great.
I tried this but with queries from different sites (in a multisite installation) and it doesn't return correct objects from the other sites using switch_to_blog to perform queries.
Do you have an idea on how to achieve that ?