I feel the asymmetry problem may be overstated. Along the short wall you could put the speakers 7 feet apart with 4 feet to spare on each side, which should be plenty to avoid strong reflections, especially if you treat the first reflection points.
I don't have any axis of symmetry in my room but am still able to achieve an even soundstage by keeping the speakers well away from side walls.
I don't have any axis of symmetry in my room but am still able to achieve an even soundstage by keeping the speakers well away from side walls.