How to prevent WP_Query from filtering on 's' but keep 's' for other purposes?

Question

I am trying to use the pre_get_posts hook to replace WordPress's search function with my own, so I want to unset $query->query_vars['s'] so that it does not restrict the results, but I want to keep 's' as a property of $query so that I can use the get_search_query function. How would I go about doing this?

add_action('pre_get_posts', function (\WP_Query $query) {

        if (!$query->is_search()) {
            return;
        }
        if (is_admin()) {
            return;
        }
        $q = get_search_query();
        if (!$q) {
            return;
        }
        $search_parameters = array("q" => $q);
        $search_parameters = apply_filters('custom_search_parameters', $search_parameters);
        $search_results = custom_search($search_parameters);
        if ($search_results) {
            
            unset($query->query_vars['s']); // This causes get_search_query() to no longer work, but omitting it restricts the results.
            $query->query_vars['post__in'] = $search_results['post_ids'];
            $query->query_vars['orderby'] = 'post__in';
            $query = apply_filters('custom_search_query', $query);

        }
});

Answer 1

It would appear that I can hook into the get_search_query filter to restore the result of get_search_query() to what it was before I removed 's' from query_vars. This operates the way I want it to on the particular site that I am testing it on, but I am not sure if this s property is used in other ways that I have not considered, so even though this works in the current circumstance, I'd be glad to hear of alternatives that don't involve unsetting 's'.

add_action('pre_get_posts', function (\WP_Query $query) {

        if (!$query->is_search()) {
            return;
        }
        if (is_admin()) {
            return;
        }
        $q = get_search_query();
        if (!$q) {
            return;
        }
        $search_parameters = array("q" => $q);
        $search_parameters = apply_filters('custom_search_parameters', $search_parameters);
        $search_results = custom_search($search_parameters);
        if ($search_results) {
            
            unset($query->query_vars['s']);
            add_filter('get_search_query', function ($search) use ($q) {
                $search = $q;
                $search = urldecode($search);
                $search = strip_tags($search);
                $search = filter_var($search, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH);
                return $search;
            });
            $query->query_vars['post__in'] = $search_results['post_ids'];
            $query->query_vars['orderby'] = 'post__in';
            $query = apply_filters('custom_search_query', $query);

        }
});