Given what you wrote, I think you will be happy with a frameless pack. An "exo" or any of the SMD or ULA framed packs will probably be an overkill -- although the only way to know for sure is to physically try them out.
For me, I would look for the frameless models from Golite, MLD, ULA or Zpack. The first three utilize Dyneema, which is pretty light and pretty darn strong. But if you exercise a bit of care, a silnylon pack can last you many seasons as well -- and they are lighter and tend to be a bit cheaper. Cuben is the lightest of all, but also the most expensive. Try to select first by material, then by pack volume.
Here's something that sounds radical, but really isn't. Once you've narrowed down to the final 2 or 3 -- feel free to buy them all -- just so you can physically pack them and give them a real test (i.e. neighborhood hike). All of the companies mentioned are highly respected -- and all will cheerfully give you a refund so long as the packs remain in original condition. Your only risk, really, is postage. And these packs cost very little money to ship. Considering the investment you are making and the importance of a good fit -- I highly recommend going this route.