Received from J_Catlady at 3/8/2019 10:53 PM UTC:
I agree it's better to keep the date, but he would have to change the name of the field/column. I guess that makes sense to do. There would probably have to be some internal futzing.
Yes, in the list of banned members only the column name needs to be changed.
Resolving which date is shown when banning then removing vs removing then banning seems to be the most important part of your suggestion... and where the most internal futzing would come in.