It's a presumptive rule. It's quite telling that the golden rule needs a rule to work.
If you got something better than the Golden Rule that can also be stated in few words I want to hear it. I am not interested in reading Ethics volumes every time I consider whether my actions towards fellow humans are good or not. I like universal, pithy guiding principles; the Golden Rule being my favorite.
I am sure I can work out unforeseen circumstances and exceptions to the rule without the extra rules that you suggest.