Project management / collaboration website in WordPress?

I’m a front-end designer and have been asked by an architect to ‘re-skin’ a Google Sites project he has set up to share project images, plans and to-do lists with one of his clients

Google Sites does not allow access to their html / css templates for me to change the page structure and styles, so I’m looking for another platform

I’ve looked at project management / collaboration platforms like Basecamp and Huddle, but they seem too complex and I really want a simple interface with just the features my client needs

Is WordPress suitable for this or is there another platform that I should investigate?

Here is a summary of the most important features required:

1. Restricted access with multiple user accounts
2. Display text, images, .pdfs and videos within the website pages
3. Zoom or enlarge images and .pdfs to view details in drawings & .pdf spreadsheets
4. Include tables of information with column ordering i.e team contact list
5. Include savable checklists
6. Page templates need to be customizable through html and css

Thanks and best wishes,
Richard Wilding