I've decided to just make 9 different mods for different breast shapes from extreme to outrageous.
At this time I can only edit/replace the current sliders so instead of replacing sliders for adjusting breast height, width, projection, and separation. How the level 1 and level 2 mods work is essentially in direct opposition of the skinny slider (so you can't do skinny with big boobs with this mod). Unfortunately, the primary purpose of this mod is the expansion of the muscle and fat sections of the body triangle.
No Mosaic / Censor Mod for The Sims 4 - Toddler Compatibility Update! Additionally some meshes/clothing will look strange with larger breasts - this is not something I can fix, and, again, is due to the way the clothing is built.