The thing about oranges is that without the sweet, they're sour. Well, what do we have that'll eat up all the sugar?
I think you may have to backsweeten once you're finished fermenting (in fact you may have to do so quite a bit) but I'd bet that it'll be quite good
In my head it comes out sort of like orange-ade.
I was going to say, do it something like a skeeter pee - little invert sugar, ferment, add OJ concentrate and nutrient stepwise. But hey, if the yeast are going like you did it, you're on the right track!