Create a custom Mac and Windows Dropbox Sync Client

We have a few special requirements for the way we utilise dropbox for business. We would like to create two clients, one for Mac and one for Windows, both based on the standard dropbox SDKs for those platforms. Functionality is almost identical to the standard clients - we just have a few extras. Please indicate your price to take the existing SDK and build a standard sync client the replicates all of the existing client features. Place a combined bid for both platforms. We will select the best parties and let them know what extras we require and you can adjust your price accordingly.