I have being playing since 2012.. so I have enjoyed the mode.. now this days the healing power of the zergs is too much.. In a way make the siege weapons ineffective against large zergs.. specially when your team is outnumbered... I would love for the siege to be way more potent against big groups of players.. just to have a chance if outnumbered..
The second I would personally love in WvW is maybe some sort of "once per week Pve intervention.. maybe a Brand Army invading they hole map {veteran troops with their commanders} causing trouble all along the map and even capable of capturing towers and castles.. It would be a real challenge to have this kind of scenarios with the heavy pvp involved already..