1) War Spying: War spectators cannot donate to war castles... this is a good feature. To take it one step further, it would be nice if they were unable to view a base's traps and donated troops as well. This eliminates issues with 'war spying'.
To cut down on war spying, either make your clan invite only or closed through the duration of war. Spying is a legitimate tactic during clan wars, you just have to protect against it.
2) Complaints On War Loot: I think the war loot regarding gold, elixer and DE is fine. Having played other interactive games that are similar, I'd recommend giving gems to the winning team as well. (30, 50?). Not sure on the number, obviously would not need to be a lot of gems, but enough to give people an incentive to try harder at wars from a team standpoint.
I'm thinking between 5 and 15 gems, any more and it would get unbalanced.
3) War Base Layouts: Would be nice to be able to save 2 or 3 versions of a base for quick upload. This may be better suited to apply to regular base layouts (farming vs trophy mode), that could then be applied/sync'd with a person's war base.
Already suggested by Mastermind, search up his thread and check it out 