Not trying to rush you, just hope that we could get the ability to mod Cold War Iron Curtain. Really wanna make some alt history paths for these nations.

You should be able to do that already. You would need to create the custom start dates/ideologies for this mod in your own mod, as it currently stands, should you wish to change the countries themselves, so that the countries have access to the correct start dates/ideologies the mod uses.

But if you just want to add new focus trees, then just type in the tag for the nation you want to add a focus tree for, and the game should do the rest.

You may need to edit your mod's .mod folder to overwrite the mod's files if it doesn't do so by default.