Possible to order over current stock value in order to combine stock products and non-stock items

Scenario:
When ordering chairs from a furniture company, the customer wants to buy 6 dining chairs. He finds the chair he likes, sees that they are in stock, and attempts to add 6 of them to his cart. However, the furniture company only has 4 chairs in stock, so he is refused to order 6 chairs, and can only add 4 chairs to his cart. The furniture company has a 3-4 week delivery time for items out of stock, but since there are only 4 items in stock the customer won't be able to add more than those that are in stock. The customer is however willing to wait 3-4 weeks for the last 2 chairs and get the first 4 delivered straight away.

What's possible atm:
Use Commerce Stock 7.x-1.x and use the "disable stock" functionality so that the stock level never prevents the customer from ordering 6 chairs. The downside to this solution is that the customer doesn't really know what to expect in terms of delivery time, and there's no easy way to explain it either. The 4 chairs that are in stock aren't deducted from the stock level automatically either.

In short: The end customer should see the amount available in stock, be made aware that any order containing more than the available (in stock) products will result in a longer delivery time.

Problem to be aware of
The order should probably create two different line items, one containing the products that are in stock, and one that contains the products which aren't (even if both are referencing the exact same SKU/product). Otherwise administration of the order will be hard, and we need this in order to handle other rules as well (such as refill stock automatically if the order is cancelled).

So.. is this possible in 2.x-branch or would this be a completely new feature request?