In the effort of finding creative ways of using old vanilla mechanics I accidentally managed to pull a new trick...
Never mind the placeholder icons, you're really seeing 9600 "soldiers" although they are much less for the game logic (sorry, I didn't break the hardcode).
A full stack in huge units will cause CTD even on very powerful PCs, large is as much as it can be handled.
It will need more testing but we're considering this for a generic rebel unit.