Okay, ive found a Solution - it was there right in front of me the whole time.
A perfect way to get this to work with Kingdoms Mods on Steam is the following
1-rename Americas to Americas_backup in your Steam\Steamapps\common\medieval 2 total war\mods.
2-rename [MOD NAME] to Americas, now when the launcher loads, and you select Americas, it will launch your mod, mine for example is Third Age.
3-Go into Steamapps\common\medieval 2 total war, create a folder entitled backup, now drag and drop your Launcher.exe and Medieval 2.exe into this folder. Now rename Kingdoms.exe to Launcher.exe, now Steam will by-pass the launcher (here is where it gets slightly more tricky)
4-Now, download the Kingdoms Cine-Ed, and follow the tutorial to install, making sure that all of the path files are correct, and the .bat is edited to launch launcher.exe (both edit and render)
5-right click Medieval 2:Kingdoms on your My Games page under Steam. Select Launch Options. Now enter into this box:
(Editing stage)
launcher.exe --features.mod=mods/americas --io.file_first @americas_cine-ed_edit.cfg
(Render stage)
launcher.exe --features.mod=mods/americas --io.file_first @americas_cine-ed_render.cfg
enter the one for which you will be doing i.e if youre rendering use render - obviously.
6-if you want to play the original kingdoms games, or any other kingdoms mod, just un-do everything you have done (get the 2 .exe's out of the Backup folder, and rename your launcher.exe to kingdoms.exe again. Also remember to delete the launch options. And if you want to play Americas, remember to rename Americas_backup to Americas again.
Hope this helps everyone, I know I was over the moon when the editor launched