Those are actually some good ideas metatronx.
I was already planning on grouping, but not the invisible node creator. That is cool.
My point for this test is actually to test the CPU usage of the AI by creating unreal circumstances, like 1000 objects with AI. Grouping them at this point would be counter-intuitive.
I can do the thing with the nodes, but would it not cause more CPU usage that each 1000 units are requesting a path to that point? Though, I do think you are right. Whenever I make all 1000 units find a path that doesn't require avoiding obstacles, they all find a path and move at the same time. Once there is a path required, they start to move at a pace of about 10 units per second, which makes the units look like a smooth river with good coding. The units only start moving on the path once the "path to" has triggered as a path found.
So it may indeed help increase how many units can move at once to a far path by using an invisible unit to create nodes on the way to the path, but it could create choppiness as all 1000 units try to find a path to the next, nearby node, on every node they reach. I will do some tests.
Here is an example link, follow these instructions first.
Test your theory and you will see it works.
To test my problem,
when game starts, click near the entrance of the spiral.
All units should move ok to that spot.
After they arrive, click inside the spiral.
They will form a river and start moving towards that spot.
While they are moving, try clicking outside of the spiral near an open field where no obstacles exist.
The units that had not found a path yet will move there first, then find the more complicated path after computing and then move back to the inside of the spiral.