Trade orders and discount management

I have the price lists sorted and have added a free delivery discount via discount management for over £200.
The problem is it calculates the delivery discount once the cart value reaches £200 and not the sub total –

Therefore it is discounting before trade discounts have even been applied. This confuses customers and It should be calculating delivery discounts once the subtotal reaches £200 I.e after all other trade discounts etc are deducted.

Editing in discount management gives options under requirements but the dropdown box does not offer ‘subtotal’ as an option.

The real fix would be to have the cart value show the discounted price and not the ‘before discount’ prices.
This current situation causes confusion as customers ask us why the cart is charging full price, because the combined discount total is often missed. Also if the cart showed the discounted prices it makes the customers job easier to mark up and see the exact price after discount individually