Actually, the Stormlands can muster about 30,000 troops if I remember correctly. Their thing is the fighting mentality I believe. In this scenario the Tyrell's would be the strongest in sheer manpower because according to the books the Westerlands don't have a working gold or silver mine anymore. So the Westerlands I don't think they would have that money backing them if it's been four generation, at least, I would think. In terms of manpower I believe its The Reach 80,000, Westerlands/North 50,000, Riverlands at 45,000 , Iron Islands at 20,000 Storm lands at about 30-35,000 and I can't remember the Vale or Dorne. I might end up getting the short end of the stick considering most fighting takes place over the Riverlands lol.