I think that death alley may be avoidable. Both on the left and right there are opportunities (albeit limited) to ladder up. The one time I actually got up from the roofs on the left side, there was a balcony area with enough room to fight on, and a staircase going straight up to the (second?) major group of flags. The right is a bit harder, but some clever siege laddering could sneak some people in.
Of course either way would probably be suicide without a large amount of people throwing themselves at the ramp for distraction.