I've done a blind jedi before so that's not hard to do for me. 

Though I meant with teetering on the edge is that they have and still are willing to use dark side force powers as they've lived a life of combat and war, as you mentioned, and understand that using such powers are a way of fighting fire with fire. The only problem is he would retain the certain flaw that all have that force users believe using a certain "side" can make you go that way. 

Or I could do a Jedi who was able to escape the Dark Side and has an understanding that force is only truly evil when your heart was that way. 

I has plenty ideas for a unothodox Jedi that doesn't mind meddling with Dark Side Powers but doesn't go nowhere as far as an actual Sith User who only trains and medidates within the dark side of the force. I am always quite fond of Jedi or force users that walk that line or dabble to gain a better understanding.