[Zooko]

Those are good objections, PhilD, however there are good responses to each of them:

*) one could design the interface so that a buggy mod could (more or less) never break the game. Python starts by being memory-safe, so you're already safe from memory mismanagement. You can make the mod single-threaded, so you are safe from multithreading issues. You can offer only a limited ability to manipulate the game (basically just "this creature moves", "this creature casts this spell", etc.).

*) the game would be a programming contest only if you got to use your own mod and your opponent didn't get to use your mod. But that's not the idea. Rather, it would be just like the current modding system: the server would have one or more mods configured at the beginning of the game and all players would have access to the same mods.

In the simple case that AI mods are invisible to the player, this would just mean that the behavior of your battle mages would depend on what mods were configured for the game, rather than being the default battle mage AI.

In the more complex case that players get to choose specific mods for specific units, at least all players would have the same options.