Deon requested that one of the things I look into would be depth of field although Gerome decided to also look into this in After Effects. I managed to find a nice tutorial ob Vimeo: http://vimeo.com/29414230
It was a lot simpler than I had imagined as it only required 3 nodes, shuffle, shuffle copy and Zblur. It was important that I had rendered in passes in order to have a separate Z Depth pass.
This allowed me to change the focus between the foreground and background although one thing I need to look into is be able to choose where I want to change the depth of field. I learnt from this tutorial that the Z blur node should always come last since if it comes before, the foreground image will bleed over the edge, at least the shuffles prevents that from happening.
Update: Unfortunately it has been decided that Nuke will not be used for the film. Due to the fact it is a software that is new to us, Deon thought it was better suit if we used something we already know like After Effects. Since Gerome and Deon having been compositing with After Effects for years, they’ll be the one compositing the film with After Effects.