Prestashop Multistore - local product attributes cost overwritten by default shop

My question is related to already solved issue where saving product in "All shops" context made prices in all shops the same no matter the currency. So if product in Poland would cost for example 100 PLN, then in Germany 100 EUR and in Great Britain 100 GBP. Link to this topic:

Prestashop Multistore - local store prices are overwritten with price from default shop

Anyways the provided solution doesn't cover this very same problem of product combinations additional costs. So I want to ignore those fields when saving product in "All shops" context.

Does anyone know how to solve it??

I achieved it by editing overriden Product.php (from /classes/Product.php) - funtion updateAttribute (around line 1800+). I took it's body, except return, into an if statement:

public function updateAttribute(...) {
    if (Shop::getContext() == Shop::CONTEXT_SHOP){
        // function body here
    }
    return true;
}

Now when saving product with combinations in "All shops", it's not updating product attributes (additional price, stock etc.) - those can only be saved in context of specific/selected shop.