Show product variations on the product category and shop pages - wordpress

Question

I'd like to display product variations for some (not all) variable products on the shop and product-category pages based on a custom field I'm planning to add to each variable product. To keep pagination working, I can hook in to the woocommerce_product_query hook in WC_Query::product_query($q) but I can't figure out how to modify the query to give me what I'm after.
The logic I want to apply is:
//Pseudo-code
$loop = $query->get_all_products // i.e. not just for one page
foreach ( $loop as $product) {
if ($product->is_simple) {
display_simple($product)
} else {
$variations = wc_get_products($product->get_children());
foreach ($variations as $product) {
if ($product->custom_show_on_archive_pages) {
display_variation($product)
}
}
}
}
The problem with the above (apart from being pseudo-code) is that it assumes we have an array called $loop but actually we have a query object.
My ideal would be to modify the query so that it generates the results as per the pseudo-code, and then my archive-product.php template can use an if/else to display simple vs variable products.
Something like this in my functions.php:
add_action( 'woocommerce_product_query', 'show_variable_products');
function show_variable_products( $q ) {
$meta_query = $q->get('meta_query');
// Do something
$q->set('meta_query', $meta_query);
}
I'm wondering if I need to actually run multiple queries somehow:
The original query but filtered to parent products
The children of these parent products (i.e. the variations), filtered to those with custom field checked
The original query but filtered to simple products
Merge (2) and (3)
Would this be possible?
Alternatively, is there another solution (that does not involve buying a plugin)?