The single-player side of CloD has many "locked-in" features. The mission maker is mainly responsible for setting loads of the parameters which the player cannot change. In many cases, you have to edit the mission file directly in order to change certain values.
The best bet for customisable game-play is to get online.
If you don't want other humans playing against you, you can always host an online map that is locked / pass-worded.
|