I think it would be better if the number of players fielded would be based on the number of losses incurred. If there aren't enough cards in the vault, then let them field less players. No 3-player teams returning to four players and such. This way, all these "stay in this sweet spot" shenanigans will be stopped, and you'll give more incentive to winning. Could be balanced by making card discards based on your "extra cards" but all balancing could be thought out by the more experienced war people here. 
for that to work, all rounds would need to make you lose the same amount of cards, so no more 12, 18,24, 30. Maybe starting at 24 but staying there could be ok, but I am not convince if it is a good idea or not. Also, the whole auction on players would need to be blown away (for snake selection?) because you can't ask a team who paid 25 more cards then another to field the same amount of deck.
On the war rule for subbing now... I don't feel there is much to add in the fact any of you don't like that rule, we got that and warmasters also. I gotta say that this wouldn't be talked half as much if we had lose any of our matches. Also, no one have mentionned that last round event helped the 3 other teams (giving em 4 cards of they're choice) which we couldn't take. I interferred once in chat about it and it was to say that solutions must be taken here and that personal hatred is bad for the community no matter what. I still believe that so I hope we will only see constructive solutions for war 6, I'M all about that too.
For my personal solutions, I doubt having a max of sub can work, some teams have a member or two that go m.i.a so the whole team would die by this, and if I go unlucky and face someone 12 hours apart from me a couple of time I won't wake up at 4 a.m. for a match. That being said, I have merge some ideas, how about you can elect not to salvage once no matter when in war, if you try to do that two rounds
in a row, you're opponent decide for a 0 or 6 card salvage and that whether there is a sub involved or not. I'd also give access to team to get rid of regular member to put em in support team and the opposite at any time in case the general can prove the member is inactive.