Combine two WordPress Queries and append the results to the final query

mergedQuery.php

<?php

/**
 * Combines two WP_Queries, and appends the second to the first
 * @author: Alex Standiford
 * @date  : 6/20/2017
 */
class mergedQuery extends \WP_Query{

  public $post_ids_to_merge = [];

  public function __construct($query_args, $primary_args){
    parent::__construct();
    $this->posts = [];
    foreach($query_args as $query_arg){
      $query_to_merge = new WP_Query($query_arg);
      $this->posts = array_merge($this->posts,$query_to_merge->posts);
      $this->post_count += $query_to_merge->post_count;
    }
  }
}

mergedQuery_example.php

<?php
//This example creates a query that will display all upcoming events first, and then display past events afterward
$webcasts = new mergedQuery([
  //Query 1
  [
    'post_type'      => 'tribe_events',
    'posts_per_page' => 5,
    'tax_query'      => [
      'relation' => 'OR', [
        'taxonomy' => 'tribe_events_cat',
        'field'    => 'slug',
        'terms'    => 'webcasts',
      ]],
    'order'          => 'asc',
    'orderby'        => 'EventStartDate',
    'eventDisplay'   => 'upcoming',],
  //Query 2
  [
    'post_type'      => 'tribe_events',
    'posts_per_page' => 5,
    'tax_query'      => [
      'relation' => 'OR', [
        'taxonomy' => 'tribe_events_cat',
        'field'    => 'slug',
        'terms'    => 'webcasts',
      ]],
    'order'          => 'desc',
    'orderby'        => 'EventStartDate',
    'eventDisplay'   => 'past',],
],
  [
    //Additional args for resulting query
    'post_type'    => 'tribe_events',
    'eventDisplay' => 'custom',
    'start_date'   => date('y-m-d m:i', strtotime('-1 year')),
  ]);