Choice of sugar, in general, is a huge factor in my opinion. Your approach is a great idea since it also addresses the lack of flavor that often accompanies cider made from grocery-store juice.
I've played around with corn dextrose, tapioca dextrose, clear rice syrup, tapioca syrup, date sugar (dehydrated, powdered dates), cane sugar, honey and agave. I mostly stick to tapioca dextrose, cane sugar, honey, and date sugar in descending order of quantity. The clear rice syrup is excellent, but expensive and hard to find. My only gripe with apple concentrate is that it is almost always from China.