Hello All,
Virtumart doesn't support Packs or Bundles of existing products.
Here is an idea to handle this, but i'm clearly not able to do this.
The cart would no longer be composed of products, but of mini-carts! (or maybe both).
A mini-cart can have one or several products.
The flypage no longer displays a product, but a mini-cart (composed of one or several product) and the add-to-cart button send the mini-cart to the cart .
In the back-end you can decide which products compose the mini-cart (maybe with a system like related product or extra ids), but for quantity option it would be necessary to add an imput or a quantity option box for each extra id.
(tips:currently extra ids take the quantity options of the product with this id)
So now, the cart checks the stock of the mini-cart and the mini-cart checks the stocks of it's products, and when the cart verifies product_in_stock and quantity, mini-cart verifies product_in_stock and quantity of it's products before, and then transmits them to the cart.
In addition all marketting options are relative to the mini-cart.
(so you can do what you want: buy 3 pay 2, discount, etc).
So now if a real developper or the core team is interested......