Custom Wordpress Theme or Plugin

Project is for the development of a custom wordpress Theme or Plug in- I am honestly not sure which. I am looking to create a wp plug* in that creates a special page, whose formatting will be different than the blog theme. It will need the ability to add images, video, and downloadable files such as jpegs, pdfs and docs but in a set layout. It will also have the ability to display blog posts. There is a mock up attached - a set layout is fine for the first version, however if it is just as easy to make it configurable by user, that is great, though not required. The user may not want to display every category [for example, they may not have video.... so ideally they can not select to display that, without it leaving a big gaping hole in the layout. I would like to build a simple version, with the ability to enhance it in a future version ... so it ideally is scalable. *it could be that it is a theme with a prebuilt set of plug ins configured within it. However it must be able to be an add on to an existing theme. Even if done via a redirect plugin to this new page. This plugin or theme is intended to be sold, not just for my use... so must be configured for download and easy to install by a user on their blog.