He can just as easily train a new pure tbh.
And then the question is: on which account do you want to have the skills, quests, untradables, diaries. A pure doesnt need a lot of those if you have a main imo.
Also you already have 2 defence
That's why i'd make this into a main and train a new pure on the side.
One more thing: during the grind of a pure you can pretty much always do some pking as long as you train the stats equally. You can try different builds along the way. With making a main this is different