Sunday tags

I need to write my own tag to Sunday. I just read one tag fic which left out Elizabeth and Radek. The author was wondering if she should add Elizabeth and Zelenka, but was told by reviewers they didn't think it was necessary and would mess with the flow of the story. I stopped reading as soon as I realized particularly Elizabeth wasn't in the fic so I have no idea what it would do to the fic if she and Zelenka were added. I really should add Zelenka too in my very vague tag idea.

Some small spoilers for Sunday & Submersion under the cut. ( spoilers )

BTW, what does YMMV mean?