So, if i get it right, the option for the defender to choose the weekly vulnerability window will be removed. Basically, for w-space small corps, CCP basically replaces the POSes which have automatic strong defenses with citadels that have weak manual defenses and must be manned and have a defense fleet ready within 2 days from the time the attacker chooses. Because any small corp made of people who have jobs and families can afford to spend a few hours whenever a group of high-school kids decide to attack their structures.
EDIT : after Steve Ronuken explained ( thank you ) i have reviewed the recording of the presentation and indeed the defenders do lose the capability to choose the weekly vulnerability window for shield attack, but they choose the time for the armor attack and the time and day for the hull attack. How this influences the wh life is still unclear a bit because i am not sure if the services of the citadel can still be used after shield reinforcement and before armor reinforcement ( i.e. enough for someone o take out his valuables ).