What you're probably after is a tree view, and possibly a sub-classed treeview. It allows indentations, like windows explorer, probably some checkboxes, etc. And if you subclass it, you can add extra interfaces (like list boxes, text boxes, file dialogs, you name it, on any node).
I have just finished doing similar, using a 'cloned' Featuremanager type interface, except instead of giving the user access to sketch/extrude/mate type features in the assembly, giving higher-level 'component' features, that drive VB code to update all relevant components and mates.
Yes, as an interface, you could say it is a tight squeeze: but maybe thats a GOOD thing. I just ported it over from a previous form-based interface, which grew too large allowing access to all the features: you couldnt see the darn assembly underneath.
Yes, tried porting the single-form into a tabbed form; but with real-time error-checking, I was unable to show the user the 2 (or more) conflicting values if the values resided on 2 (or more) tabs.
With the tree view, I just save which areas of the tree are expanded (you listening, Solidworks ?), scrunch everything up but the conflicting dimensions, and show just those areas expanded. After the user makes his corrections, I return the user back to the original tree view state.
Not to mention that the user is already familiar with the featuremanager-type interface....