I think we did something similar in one of our projects. We created a custom wizard to add additional data input fields.
if you want to auto fill user,organization or context, I remember we have it OOTB. But for custom objects, you will have to create a suggestion class (implementing Suggestable interface) which would basically do the query. This class should be registered as a service, This service could be called from suggestTextBox wrapper tag.
Thanks
Binesh
Barry Wehmiller International