I would find 140mm cranks OK if that was all I had ever ridden.They seem to work ok plus it's not that easy to get 105 stuff any longer than 175 or at least 175 is commonly available.
Your bike doesn't fit in the way a med bike fits a med rider. You have never ridden one that fits well because no brand makes them. The only source of big, well proportioned bikes for very tall riders is US custom maker Zinn.