AbleCommerce: Force Separate Shipments for some products

We take advantage of an AbleCommerce setting in order to do this. Each product has a "Shippable" setting and that setting can either be: No, Yes, or Separately. Our code puts any product with "Separately" specified in it's own shipment. The default behavior for AbleCommerce is to treat products with Separately specified as shipping in a separate box but not as a separate shipment and if there are 2 of the same items, they won't even be calculated as being in a separate box. 

I defined these functions in App_Code/BasketHelper.cs

public static void BreakupSeparateShipments(ref Basket basket)
{
    //returns a list of all shipments, having it as a separate list lets us manipulate basket.Shipments without breaking the enumerator
    var list = basket.Shipments.FindAll(x => x.Items.Count > 1);

    foreach (BasketShipment bs1 in list)
    {
        var itemList = bs1.Items.FindAll(x => x.Shippable == Shippable.Separately);
        //iterate through items that ship separately and put them into separate shipments
        foreach (BasketItem bi in itemList.Where(item => item.Shippable == Shippable.Separately))
        {
            if (itemList.Count > 1 || bi.Quantity > 1) 
            {
                if (bi.Quantity > 1)
                {
                    int q = bi.Quantity;
                    bi.Quantity = 1;
                    bi.Save();
                    //Move all but one of the items to a separate shipment
                    for (int i = 0; i < q - 1; i++)
                    {
                        var newBi = bi.Clone();
                        newBi.Quantity = 1;
                        newBi.BasketId = basket.BasketId;
                        newBi.Save();

                        foreach (BasketItemInput _BasketInput in bi.Inputs)
                        {
                            BasketItemInput newInput = new BasketItemInput();
                            newInput.BasketItemId = newBi.BasketItemId;
                            newInput.InputFieldId = _BasketInput.InputFieldId;
                            newInput.InputValue = _BasketInput.InputValue;
                            newInput.Save();
                        }
                        basket.Items.Add(newBi);
                        basket.Save();
                        PutItemInSeparateShipment(newBi, bs1, ref basket);
                        newBi.ParentItemId = newBi.BasketItemId;
                    }
                }
                else
                {
                    PutItemInSeparateShipment(bi, bs1, ref basket);
                }
                    
                //if (bs1.Items.Count == 0)
                //    basket.Shipments.Remove(bs1);
                //bs1.Save();

            }
        }
    }
    basket.Recalculate();
    basket.Save();
}

public static void PutItemInSeparateShipment(BasketItem bi, BasketShipment bs1, ref Basket basket)
{
    BasketShipment newShipment = new BasketShipment();
    newShipment.BasketId = basket.BasketId;
    newShipment.WarehouseId = bs1.WarehouseId;
    newShipment.AddressId = bs1.AddressId;
    newShipment.ShipMethodId = bs1.ShipMethodId;
    newShipment.Save();
    basket.Shipments.Add(newShipment);
    //newShipment.Items.Add(bi);
    // assign this basket item to the new shipment
    bi.BasketShipmentId = newShipment.BasketShipmentId;
    bi.Save();
    // reset the parentitemid value since now this item is its own basket item record
    bi.ParentItemId = bi.BasketItemId;
    bi.Save();
}

I then the call BreakupSeparateShipments from the Page_Load method of the ShipMethodPage.ascx.cs but if you're using the OnePageCheckout method, you'll want to call this from the basket initialization area of OnePageCheckout.ascx.cs. 

Acknowledgements: Joe Payne provided some insight for this approach and I was able to use some of his code from his post for shipping all items in an order separately in order to resolve some issues I had with my code.