You want your playerbase to return? and save the pvp aspect of the game?
Remove every hot/pof aspect from wvw and pvp too, and rework everything. Just leave revenant.
First rebalance core classes, meanwhile old veterans and new players can enjoy or experience what gw2 was when it all started. That would motivate older players to come back, veterans to be more active and new players to understand better about game's fundamentals.
After you succesfully find a nice balance between each class, add gliding to wvw and hot specs, and start reworking them towards a good balance between core and hot specs. Imo the best times i ever had in wvw were just after hot patch, when people had the choice to use either hot or core specs and still have a good time, tons of builds variations around the map making interesting fights. And taking back chrono changes!!!
Now, personally, i always hated pof, i think specs in that expansion aren't as good as hot ones, some designs are good others feel rushed, but i know a lot of players really like em, so with some reworks like tuning down FB, buffing renegade, removing DE from game, giving SB either less damage or less mobility, removing holo forge spam and sustain overall, reworking mirage evades and passive damage and reworking scourge from scrap to give them something else to do than beeing an aoe field with legs. Implement them again in wvw.
Only thing i'd remove besides Deadeyes (unfun mechanics to play as or against that ruined thief because of core/hot insane uncalled nerfs) is the warclaw, imo warclaw never should have been added to this game mode, it ruined the small scale aspect of the game, and also the big scale battles, because of how easy is to run back to defend something, making ninja takes impossible, and large battles really chaotic and really loooong and tedious (between the FB meta and the speed factor)
If you add it again, please add a dismount skill, or remove the warclaw's healthbar, so players that stay mounted die if they can't escape quickly.
Also an idea to rework wvw.
Remove all existing wvw maps before alliances launch, then select pieces of the pve map, copy them in to another instance and make alliances choose a starting point and make them fight for territory, after a week the alliance with more terrain wins, after a few months the alliance with more wins get a prize for every player in it.
Can you guys imagine? siege battles in castles in the middle of the floating isles in verdant brink? or in the middle of the forest in auric basin? pof maps look really good for this too.
You can even change maps every time you want and make wvw players travel all over tyria fighting for territory. And it could give a more rvr like feeling, where players fight for something more than themselves. Current wvw feels like a huge grind for pips or reward tracks, and fightin all this years in the same places is getting kind of boring.