I'd like to have customization groups, whereby I could define what sounds and bubbles and notification icons get used for different groups of people (family, close friends, work colleagues, etc) and then I could add phone numbers to those preexisting groups.

I know that I can customize each number, and customize multiple numbers at a time, but if I forget a family member or acquire a new work colleague, I have to manually configure their number the same as the existing ones.