If you use structure blocks to create the jigsaw file would it be possible to stack other structure blocks within it? So on the off chance it did generate and you discovered it you could load the structure blocks contained within the jigsaw generation to create bigger structures. Providing of course that you add the extra structure files to behaviour pack for that world. If this did work the possibilities are literally endless.
Im currently experimenting with a road/rail construction pack including tunnels and bridges on bedrock. Idea is you can you load up the behaviour pack in any world and build a network system for your world by placing just 1 structure block. The rest of the building options are presented to you in way of more structure blocks each time you place a new segment.
The thought of implicating structure blocks in world generation is very exciting. The chance to generate stacked structure blocks is mind blowing.