Design a pizza delivery app

We are a white label app reseller company and are currently working on a new product: personalized pizza delivery apps. We are looking for a designer who will be able to take an existing business, understand the design idea behind this business, and be able to translate this idea in the design of a customized app for the same business. Basically, we have built a pizza delivery app and we want to resell it to different pizza restaurants, each time with customized graphics. We are looking for a designer who will be able to do this for us. The job is not a one-time offer, but an offer for all the apps that we will be developing in this category. The work itself is not so difficult. There is no need to create elements and graphics from scratch, only to match color themes and incorporate existing logos and elements that the restaurant is already using. We produce our apps on both android and iOS so the design will have to fit for both platforms, or two different designs will need to be provided: one for iOS and one for android.