Is it possible to create a custom list column whose type is a custom content type? Not just a column from that content type, but the whole item itself, or even a list of that content type?
My goal is to create a hierarchy of content types, for example:
My Prospect Content Type -> Has column : Client (of type My Client Content Type)
My Client Content Type -> Has column : Associations (a list of type My Association Content Type)
I ended up trying out and liking the solution presented in this article.
The gist is that I create a content type "My Parent Content Type" which inherits from the built-in Folder content type. I create a second content type called "My Child Content Type" which simply inherits from Item. Then, I create a list which can hold items of both of these content types.
Next, I add a My Parent Content Type to this list, navigate to the item I just created, then create a My Child Content Type item within that folder. It works well enough, I think. The only trick is, I need to make sure the site users only create new items in this manner.
I would like to constrain the New Item button to only allow creation of My Child Content Type items within the context of a My Parent Content Type folder, but I suppose that is another question related to Ribbon modification :)