You probably have the option to replicate schema changes set to false.

So this may have to be taken into account when the devs add columns in future as you may have to add the column both sides.

I think you can change the setting in the publication properties so that it will do schema changes both sides if added on publisher.

Do this in test first before putting on your shades and unholstering your magnum.

Decision as to what to do in the case of columns not existing comes after having a chat with the devs who might have an idea of what the environment supposed to look like.