Plan to use sharepoint sites as work areas for engagements. Each engagement will have its own site( just one site per site collection because the site size can be > 2 gb and can have 100s of such sites).
All sites will be created out of a common site template but will have context sensitive web parts to setup data.
I am not sure what kind of site template to start with in trying to build out the final site template. The requirements include some libraries for documents some custom web part pages etc and also security trimmed navigation. Any suggestions on what site template to start with?