I'm pretty sure a PVE Version does exist in game. Just it's rare or not many people have found the way to get them. When I was around lvl 16 I saw a lvl 17 Sith Marauder dual weilding a red saber and a purple saber. I have no proof of this.. but the Dev's did state in the Q&A that purple crystals are out there, you just have to work for them, I don't think they'd limit them to PVP at 50, nor do I think buying a PVP box is exactly 'working for them'.