In the end, this is an MMO. It is based in the Star Wars universe, but it still has to play like an MMO. Giving a ranged class melee abilities is a problem.
Well, I wouldn't worry too much about balance over this. My gunslinger whacks people over the head all the time with the back of his gun without people crying "Foul!".
Balance obviously needs to be concidered but that is more determined by the ability itself rather than the fact that it is activated within melee range. We ain't asking for a Maul type of damage, just something, anything, that could be activated with the saber, mostly for the feeling, not as a class buff.
It could be that a saber attack caused accelerated metabolism on the target, causing the remaining Affliction ticks to tick every second instead of every third.
I can't picture every sorc/sage suddenly rushing into melee range over that. And even if they did, no one would be happier than the melee classes if they did.