Has anyone tried making graff by adding commercial beer to cider just before bottling?
If you could use a beer gun to bottle I bet it would work. If you are just pouring it in, you might end up with a semi-carb'd concoction. You could prime the cider to over-carb, but calculating that properly might prove difficult.
You can always blend at serving time. Take a look at the 10/31/13 Basic Brewing Video.
I would blend at serving time. But that's my opinion. Or you can just do hops in the secondary (that's all the rage right now).