I think a great feature that could be added to either WvW or on its own would be an instanced dungeon with events, bosses, traps, puzzles, multiple paths, possibly dailys, ect that is open for player combat. Kind of like the puzzle thing in eternal battlegrounds but more about doing events and killing bosses. A lot of people probably heard of darkness falls, passage of conflict, and the labyrinth zones in Dark Age of Camelot and it was a great feature. It wasn’t mandatory and had its own unique experience.
So what im suggestion is a zone that has a mix of pvp and pve that isnt WvW and more about the pve but with the threat of pvp. This would be great for players to group up and fight each other in smaller groups or even 1v1 play. The only problem would be how to reward the pvp aspects of it since as of now you don’t get much from a single player kill. Maybe the rewards for killing players could be tied to the new WvW progression thats coming out in march or have even its own progression system for killing players in this new WvW/PvE zone. The PvE rewards would be what you would expect. As far as who and what servers have access to it, maybe it would be based on the WvW pairings or even every server would have access with overflow zones or a cluster/shard system that has channels for when one instance is full so there would be no queues. And so you could get in with your friends have a group queue option and an option to choose what cluster/shard to enter.
Im sure there are a lot of other people who would agree this could be an amazing feature if done right. Any more suggestions on this topic would be greatly appreciated cause the more people who are interested in this type of system the better the chances of the devs considering such a feature.