For as long as we've had GAC there has been an advantage to attacking second. So much so that based on data mined on my opponents the majority attack most of the time in the last hour of the 24 hour period. For many players though, this is not an option and so they are put at a disadvantage. Unlike squad arena where CG has given us the option to move our payout to when it is convenient to us, players cannot choose when GAC attack phase ends. With the increasing importance of GAC due to it replacing squad arena as the main source of crystal income, it is important that CG address this imbalance between players who can set aside the final hour to attack and those who can't.
My suggestion is that during the setup phase both players have the option to hide attack phase progress. If either player selects that option, then neither players sees the progress or score of the other player during the attack phase. Only when the phase ends during review can you see the detailed results as we have them today.
I think implementing this now before the next GAC is critical to avoiding a lot of frustration and ill will now that CG has raised the stakes of competing in GAC.