Yeah, it will be tricky to figure out how to do some of those is a UI-friendly way.
I wondered: do people ever use the multiply/add/divide features?
You may or may not know that there are tedious ways to do each of these things right now in 2.8, using the widgets that show up in the Normals section of the Tools property panel (top tab on properties panels normally on right side). There’s a tricky multi-select-mode dance to specify exactly which normals to affect (which I hate). See the release notes for details.