I've successfully split the ruleset, so everything should be cleaner now. I've also added your changes ceilingrat, and updated my git repo. However, I had to force the update because I rebased my stuff incorrectly :x so beware of that.
edit: also, I took a look a the string error you got in your screenshot, and I am not sure what happened there. The string exists, so it might be something you did while modding the language files? Let me know if it persists. The string name is "STR_HEAVY_WEAPONS_PLATFORM_LC". And now that I've mentioned this, I am not finding it anymore :x but it will be updated shortly.
edit2: updated github. Now I am worried I may have lost other things :x