I wouldn't object to strengthening this to a 4 night minimum which must include Th/F/Sa night - but I don't think it would change much. If you were able to get Th/F/Sa today you could easily get W out of block somewhere at a reasonable price. Same for Sunday night.
That would be unfair to the people that can arrange to arrive Thursday morning. The Con spans 4 days, so only 3 nights are really needed. The current 3 night/Sat night stay required is perfectly fair.