If I could only have one thing, it would be the limite breaks.

Other than those, I think having additional PvP effects carry over into PvE, would be fun too. For example, Dark Knight's salted earth. That thing has like 3 additional effects in PvP. You draw nearby enemies in, you are able to bind them, standing inside of salted earth gradually heals your HP and you receive 20% less damage. Never mind, that's 4 additional effects. Maybe that might be too OP for PvE, but at least one or two of those extra effects would be nice to have.