Since we are eliminating ways players take advantage of grand arena lets not ignore the fact that there are a large number of ppl who wait till last hour to attack elminating the guess factor on thems...
It's already a "fair clean slate" each player can see opponents defenses to the same capacity, and have the same amount of time to attack. And 24 hours is also a fair and transparent length as many who play have other commitments, this time allows them to attack when they can.