Sorry, I should have been more clear. I am aware of #defaultmapzoom, but afaik changes to the map file will not be reflected in existing games. In the current situation, I downloaded a random map that had been used in someone else's multiplayer game (eventide) because I liked the layout, but I did not look at the map file close enough to realize that they had lost their #defaultmapzoom command. I assume they must have edited it in the map editor. Anyhow, it was subtle enough that it wasn't until late game that I realized how cluttered things were getting.
Not a huge deal. I will just remember to watch this more closely in the future.