Adding brands to discount will be great! As we sell multiple brands in our outlet, and currently, DEAR cannot recognise the discount by brand, instead it creates a new service product or recognise any product in our inventory that's called "Discount". It's really difficult to see the actual sales by brand and currently our Accounts Dept have to edit the brands manually.
A discount is a reduction in price, not a product.
Please check this arctice http://support.dearsystems.com/a/solutions/articles/11000035344 . It describes how you can use discounts for Brand, Category, Tag or Product.