How about when you place a factory down it automatically sets up the assist-other-factory command.
There are various ways to do that like only set up the order automatically if...
- there is a close nearby factory or
- its touching square with another factory or
- it was placed in the same command as another factory, like dragging 10 facs
90% of the time I want things assisting and that's something I need to do manually after the factory has started construction. It would be easier just to cancel assistance the few times I don't want an assist. Or I could hold control while placing the fac to not-setup-assistance.
It's just a quality of life thing.