Bottom line
When we increased the unit and formaton count years ago we considered what the vast majority of players would be comfortable pushing around and 500 units per side was considered to be way more than most would want to play with but it did allow for players to build really big games. It's inevitable that wherever limits are set someone will want to exceed that. Had we allowed 600 units somebody would want 700.
The problem with the AI bumping into the unit's ceiling wasn't an issue becasue the points limit was lower. We increased the points in WW2 to match MBT where the max points really is needed becasue of the higher tank costs.
So the best advise for the few players who are running into this problem is to keep your games within reasonable limits.
As interesting as 1000 unit assaults might be for a tiny % of the people who play it's simply not practical to tear the game apart to do it
Don