[Redgeneral]

When someone loads a mod, would it it load a custom menu system?
i.e.
At the first screen (with the clickable buttons of "new game", "options", exit) the mod sets the background, the music, the text, the logo.

For instance if I did a mod for the middle ages,
The mod would make the background that of a view of the middle ages (either 2d or 3d)
The text would be given a medieval font
The logo would be that of the mod's e.g. Dave's Med Mod
Music could be medieval monks chanting.

The information for this would be stored in a file, and called when the mod is started.

[Acumen]

Yes, the UI as it stands is completely scriptable, so you'll be able to change the user interface (including the main menu) and include those changed scripts, additional texture sprite artwork, ogg audio files, etc) in the mod pack.

Exactly how mods are enabled/disabled is something that we'll need to work out at a later date, but probably "global" mods (like the menu mod above) would be toggleable either in a mod tree toggler tool or at least in a .cfg file (it'd have to be done out of game, since the game's already loaded by the time you reach an in-game UI, and then it's too late to load the mod ).

The plan is that scenarios in turn could include any amount of "local" mod content, that's only active during scenarios in that mod pack so that it doesn't override the rest of the game.

[Redgeneral]

Sounds good