Thanks so much for the excellent feedback: 
reports are welcome! You’re right about the problems with highlighting which data is mandatory and which is optional. It’s a symptom of trying to work within Discourse’s feature set which doesn’t actually indicate which of its own fields are mandatory, but does for our custom fields. I’m sure there’s a workaround though as it’s pretty flexible.
Maybe we can change “Sector” to “Primary Sector” and add the additional options you suggested. Unfortunately, Discourse dropdown fields only support choosing one option. Then again, the Discourse feature set changes every week, so I expect more flexibility in the future.