Creating a new version of the game for your mod
AGEOD patches AACW frequently. Patches are comprehensive, and will overwrite your mod. How do you avoid this?
Go to the main game directory (the one that contains AACW.exe). Create a new folder. Name it after your mod (for example - "my_mod"). Copy all the files and folders from the ACW folder into the my_mod folder. Create a text file. Name it modpath.ini. Open modpath.ini - on the first line type "my_mod" (without the quotes). Save it.
Now when the game starts it will use files in the my_mod folder. You can create and test your mod here. You can still install patches to the ACW folder. If you want to play the standard game, delete whatever you typed in modpath.ini. It is a good idea to save copies of all modified files in another location, so that you can easily create a new mod folder for each patch.
I wanted to continue on with a PBEM game I have going on the previous mod so I did the steps outlined above. I made a Folder called BrigMod in the main game directory, copied all folders from the ACW directory to it, and made a file called BrigMod.ini. (not sure if this would work in preserving a PBEM game on a previous patch but it is a good idea regardless if it works for working on my mods and still have the vanilla game available.)
I have tried placing the BrigMod.ini file in the main game folder, in the ACW folder, in the BrigMod folder and no matter what I do it always says it is using the ACW/ mod folder in the left hand corner on start up.