I think that nothing can be done to please players who are interested only in PvE or PvP (fair) in a unscripted game mode that combines PvE & PvP one way or another.
To try and limit players or groups or raids or lvl/ilvl differences and send them to their own shards won’t be good for the organic nature of the mode itself, and would make it into a bad BG variation or just some very confusing mess.
Removing rewards won’t do any good for War Mode, because this game is built on rewards for doing any activity, so without those - even players who like to do WPvP would spend their time on other activities that can give them rewards to progress.
For players who only interested in PvE and don’t want to do anything with PvP - there is already an option. Only 10% greed prevents some players from using it.
For players who are interested in fair PvP conditions, sports-like mode, competitiveness with only equally rated opponents with same numbers - there is also options for that, and all of them provide much deeper reward/progression structure for additional enjoyment.
The core nature of WPvP and War Mode is a complete and total freedom. Not only in items/abilities usage, but also in players behavior / decisions / actions. Everybody has the same choices and options what to use, how, with whom, etc. So it is already an even playing field, where players on one side is a content for players on the other side and vice versa.
Players need a reason to be anywhere in the game, and that is where the main clash happens in WPvP. To please players who want a PvP part of WPvP to be removed or limited in any way - is to only cripple WPvP for the sake of PvE, and it won’t make any sense overall.
With all that, I see only two real problems with current War Mode, one major one minor.
The major one, technical - sharding. It very easy to abuse, it can’t keep up with overflow that happens with LFG, and it creates way too much lag.
The minor one, game-play - faction balance and incentives. I think it would be better if players where rewarded for doing War Mode and not for switching it on/off, on both sides, but without forcing players to stay in WM for a week etc. If players had something to work towards on a daily basis, and weekly, and maybe even monthly - that could be both, an incentive and rewards.
The biggest problem I think is not with War Mode itself, but with players perception. Before WM majority of servers where skewed towards one faction, WPvP is not something that was really happening in Legion, yes there were fights from time to time, but not even close to what is happening now.
Even on Defias, with as close to 50/50 population as it could be, when in Legion I attacked someone at WQ, more often than not, even players from my faction was telling me how bad this is because “he only wanted to do the quest”.
War Mode brought one drastic change - everybody knows that it’s a player own decision to click that button, and that makes that player a fair game. Plus no more one-sided servers, and WPvP started to happen again, with all it’s unfair unscripted glory.
So, all these players, who are used to little to no interruption in their World activities from WPvP, opt in to get those bonus rewards and expect the same as it was in Legion. I don’t think there is a way to please them without almost killing WPvP as it was in Legion.
I can only imagine the whine from those players when 8.2 lands - Mechagon zone shall be forever known as a Megamassacre zone. One hub for both factions and a zone with dynamic events and possibly faction controlled cannons/devices - so much fun so much freedom, and not so much for everybody, and it’s ok.