When you consider that the average person's torso is 18" high and about 12" wide, it's possible. If the rifle can maintain a minimum of 2 MOA consistent accuracy, you'll have an easier time reliably putting it in the pickle barrel. I'm not sure what the Saiga 308 can do for accuracy though. I would wager that it's at least 3 MOA or better, but how much better I don't know.
As for optics, my suggestion would be to consider going for as low of a number as you can on the lower magnification range. If you have to use it at short range (under 100yds), having as wide of field of view as possible is ideal. 3x is the highest to go on the low end, but 1x-2x would be my preference.