Installer project (MSI) for branding versions

We need a Installer solution for branding versions. Background: we develop tools that are sold by branding partners too. As there are many partners, we want to create a [login to view URL] (or .msi) for every partner. The branding in our tools is just done with a simple file in the installation directory. The only difference between our own setup and the setups for our partners is this single file. As we update our tools quite often, we don't want to create a new setup for every partner on each update and we don't want the customer to have to download the latest update on installation first. So we want always the newest version of our tool to be available for download, by just updating 1 .msi The main .msi is always on our servers available and this setup will be updated by us. So we need a solution, that downloads the main .msi and installs it and then put the branding file into install dir. This should be done in a smooth way for the user. We are using VS 2010 and VS 2012 and our tools req. .Net 2 or .Net 4 Please provide details on how you will realize this approach.