I have seen a handful of recent maps with a $1 Billion target. Even multiplayer ones. Some in the past also.

I have completed a couple such maps, they take 10+ hours of non-stop play even though I'm an experienced player. If you have an equally matched opponent, the multiplayer ones can easily take 20+ hours. Maybe some people have lots of time. But, that much?

The "no fun" problem I see is that the game coding gets laggy when engine count gets high. At 50+ engines lag is starting to happen, especially after a savegame.

Loading a savegame seems to enduce lag. So, I recommend maps that can be played in one session.

This is to say that the experience in such maps is highlighting the worst parts of the game: BAD LAG, sometimes almost freeze frame in huge games.

For the record, my PC is mid-range. I know I can clone and edit most maps for myself/friends. But, I'm suggesting that the majority of people wont know how to do this. More people will probably enjoy a map that has a more reasonable targets. :)