Mass Edit - Special Price / Price by Percentage on product tools

A great update to the mass edit tools would to be able to update multiple items special price ( or regular price ) by a percentage amount. 

Its great to be able to update products price but right now it forces you to only be able to change products with the same price since its one field. The ability to adjust by percentage would allow us to update multiple products at once. 

Use case: we have a special that is running from the 11th to the 30th of November. We want to update 30 products, but the discounts are split between 5,10 and 20 % off. I can use the sales feature but cant breakdown as much as Id like to using it as the attributes are not shared among all products and doing it by sku is very lengthy. I can multi select, then put in percentage values next to the price and set the to and from date all in one shot. Save, and voila!

Another version of this is to allow for multi update, so that rather than 1 field you get a price field for every listing that is selected. This could be a toggle if you need more fine tuning ability, so its not the default but you can click "Expand edit" or something to get this as well.