I have vendors with 1000's of products who need to be concerned with currency exchange rates as well as other things that facilitate the need for price changes in the entire store. It would be great if there was an option for each vendor to be able to adjust all prices by a certain percentage without editing individual products. This could also work as a sale feature per vendor without showing too many sale icons or marked down prices.
The best use might be increase or decrease by x% and round to the nearest $10 or $1 at the vendors choice.
I think this would be a great standalone plugin but it would be very useful in Dokan.