The thing that made pvp/combat amazing in COH was the high speed combat feel of it, which the devs didn't seem to understand, hence why they alienated the entire pvp community in i13 and caused the majority of the pvpers to leave. If you're going to do pvp in VO, please make it like pre-i13 pvp. There are other ways to make melee classes viable in a high speed movement setting beyond just slowing everyone else down. You could give melee characters abilities like ranged taunts that reduce the range of ranged characters (Forcing them to fight near the melee character's melee range.), giving them ranged root/snare cc abilities, and also increasing the range of melee abilities so that they can hit from a little further than the usual 5m range of melee abilities (Maybe 7m-10ms).
Short Version: Don't artificially limit the fast paced speed of the game in your actual game mechanics, let the players be in control and don't let the system be a limiting factor (No insane travel suppression, no insane resists, no healing limitations, no damage normalization across different power sets, etc.).
Also, Do not mix PVP with PVE, it's one of the things that caused i13 in the first place. PvP zones like RV that mixed pve and pvp, which in turn caused a lot of people that didn't pvp in COH to call out nerfs to systems they never really used outside of those PVP zones, that had pve activities/badges in them.