Simply make it the PvP equivalent of your Job's Primary Stat.
Now, a person can use their PvP gear in Frontlines for the superior stat allocation.
Removes the awkward scaling.
Removes the defensive imbalance.
Prevents PvE usage.
Gives the gear value again.
Just tweak the amount of Morale on PvP Gear to mirror the proper amount of primary stat for the items' ilvl, literally make it identical to your Primary Stat, just for PvP use only.
Please SE, what do you think?