It would be great if we could make a selection, right click and select disable diagram. A "diagram disable" structure would automatically pop out encompassing your selection.
It definitely woulnd't be too hard to make a Quick Drop Shortcut or Right-Click Plugin for this functionality that covers most use cases as GregS mentioned. I bet you would get most of the way there by just using the Enclose Selection method.
I could see potential problems when a situation comes up like shown below. In the case where you have the three subtract nodes selected, what would you want the expected behavior of a disable to be?
Maybe in the case of multiple selections across the block diagram, the selected components would grey out with a polymorphic type label under it. The label could quickly select between enabled and disabled.
