Tree different column counts by row- options?

I need advice from the forum. My application requires a way to display a hierarchical view of data where each row in the structure can have a different number of columns. It's a report previewer and I would like to add activity (add/delete columns, drill down, sort) to the columns in the future. I think there are two options: Make a delegate with a slider for the columns or re-class abstract item view/abstract model view. Which is 'better'? Are there other options? Has anyone done such a thing and would share some code?