Using caps lock key instead of right click (contextual menu) I'd like to remap Caps Lock to right click - for the cases where I can focus on objects with cursor keys, or tab. 

For instance after selecting files in Finder I'd like to hit Caps Lock and get the contextual menu you'd get on right click.
The 3rd party tool http://pqrs.org/macosx/keyremap4macbook/ seems to be able to do what you need to remap your keys.

One possibility is to remap Caps Lock to Control and thus pressing Caps Lock + left-click would open the context menu.

Sure, this doesn't remove the need for a mouse click, so the right-click might be a better solution :)