Skipping the Fiends fight would work out fine because it's mainly supposed to be a party vs party fight and if you're alone it would make sense to fight Golbez 1 on 1.
As for the item Edge gives you, how about the Glass Mask? It could be passed off as a mask Lugae used when he worked on Balnab and other experiments... Of course it would have to be nerfed a little because getting it before the moon is a little broken. Going back to the Aegis shield, you can either leave it on Kain & let it be buyable OR place it where the Defender is and move the Defender somewhere(maybe Bahamut's mooncave).
