I remember playing the sims years ago, and there weren't any qos tattoos yet. I had 0 experience modding. But I watched a couple of tutorials, which I believe took me like 15 minutes total, and then I had the 'skills' to create every possible qos tattoo I could think of. I created the one on the ankle, the one right above the pussy, on the ass cheek, etc. It's really extremely easy to mod tattoos in the sims 4. You really just need to download 1 program and insert a picture of your liking (a qos logo or whatever) into the tattoo slot. Go watch the tutorial and make sure to come back here to show us what your created.
Aside from tattoos, what exactly do you mean with bbc mods? I mean, there already are sex mods with big dick options, and there are black characters ingame. So what exactly is it that you had in mind that is specifically related to bbc?