Not a bad rule of thumb! I always overpack. I have heard of packing, then take out half. I’m not gutsy enough for that. But the pack 2 sounds like perhaps something I could do. How about a suitcoat?
One thing that might be good is lightweight nylon/polyester stuff. Can wash out in the sink and dry by morning. (I’m looking to buy a set of nylon sports underwear and give those a try for that reason.)
I have a pair of travel pants from TravelSmith. Drys in about 3 hours. On one 19 day trip I pulled out the dress slacks once.
I count the blazer as one of the jackets