I found another use of su that may need to be added to your list. rabbitmq (oddly) wraps itself up in a shell script, /usr/sbin/rabbitmq-server, which asserts the user is root or rabbitmq, and drops down to rabbitmq if it is root (using su), then starts the actual binary. The problem with this one is that it is upstream code and cannot use s-s-d for obvious reasons.