New promotion type: Threshold item promotion

There is a gap in the promotions engine which has been highlighted by several of my customers. They want to be able to create a threshold discount, which applies a discount to a specific item on the transaction. For example: Spend $100 Get Item X at 50% off. Or Spend $150 Get Item X Free Of Charge (100% off). At present you can only use mix and match promotions based on a quantity of items sold. Existing threshold discounting can only apply a $ or % value off of the entire basket, not a specific item We would need to be able to configure a threshold discount, (so triggered based on basket spend), to apply a discount to specific items in the basket, and be able to specify $ off, % off or deal price for one or more items. In order to trigger the promotion, the threshold will need to have been reached, and the item(s) being discounted must be added to the basket. Also the threshold should be met not including the item being discounted (i.e. for the Spend $150 get Item X Free of charge, if item X is $20, they will need to have spent $170, and the discount applied will be $20, to the specified item only).