The GAC system has a lot of flaws, nothing is ever perfect. However one thing that is frustrating is having a disadvantage due to timezones with GAC being limited to a 24hr window. Giving a time limit is not the problem but information on your opponent and what they probably did is. You can mostly deduce from an opponents attacks and their respective scores what they likely used, sometimes it can be a little bit different, but based on known defences you can get a sense.
Because of this advantage you can often do attacks based on this (and know what you to win on avg battles) and sometimes take educated gambles. This makes it hard for people to some times hide something in the rear because they have to attack at a specific time due to their real life. You shouldn't have to suffer or be at risk of losing because you can't hold out until they attack.
I propose that players don't know each others scores until the same zone is beaten. So if I beat top front, and my opponent hasn't attacked he can't know my scores there until his is done as well. Same with other zones. It is a simple Fog of War (FoW) system and wouldn't be hard to implement. It allows people to have competitive edge and engage with GAC on a time that suits them knowing that what they did and how they did is not a competitive advantage to their opponent.
I think there are good arguments to say not to change it and you just have to do X Y and Z better or make X Y or Z changes. These are still all dealing with the system the way it is right now.
Anyway this topic has probably been discussed at length before, I don't know. But I think this is an easy change to implement with very few drawbacks.