About the extra slots for Guild's War defensive teams i guess it's never too safe to remind about possible issues that might need to be triple checked @Sirrian : Making sure that the slots of Guild's War teams doesn't suffer/cause any interference with the already existent slots on gameplay one way or another.
Me and others are surely excited to go into war as soon as possible, but... Just to be really sure that everything is working as planned would you guys/girls, the dev's team, consider a propposal that the first week of the feature would be just a field-test?
I wouldn't dare to tell how you should work, but considering at the very first week issues could make people "waste" their attacks or having unexpected problems with defensive teams of any sort, (that already happened once at the very first stages of the new PVP) and also to provide a fair starting point for practical experimentation to all players, would consider this "First Week Test"?
During this first week everyone would receive a reward (the same for everyone) as long as they join into the Guild's War, it doesn't even need to be a GW exclusive reward of any sort, maybe 10 Gems Keys would be motivating enough. And aside from that some scores would be calculated for practical experimentation (and the said scores would be erased at the end), but no real GW reward would be obtained at all until the next week. If everything goes ok after the test of course.