- Room for 6D, 2 small/medium lenses, 1 telephoto, 1 speedlight optional.
- Some form of weather resistance
A camera and a couple lenses isn't exactly heavy packing. I'd just grab any of half a dozen old Jansports that I have laying around. With that little gear I don't need anything fancy, I think that traditional backpacks are more comfortable than camera specific ones (with the exception of really nice packs like F-stop), and I prefer not advertising that I have a bunch of camera gear.
It doesn't have the flashy camera guy appeal that some like, but I'm ok with that. I have a bunch of those free shoulder bags that B&H and Adorama give away with new cameras. I pull out the inner padding and just stuff my gear in there. I'd also grab a dry bag, you can get one cheap on Amazon if you don't own one, and keep it in the pack in case it rains. You can also get a cheap pack cover, but don't count on those things in a true downpour.
As to the tripod, I too usually just hold it in my hand. If you were doing a long hike I'd either work out some straps to attach it to the side, or try to put it in the pack and stick out the top. Ultimately though, the comfort level is going to depend more on the backpack than the way you attach it. A small little pack will never have the comfort of a framed hiking pack. Personally I'd just get a good Gorillapod - the DSLR one - unless I was going specifically for some tripod shots.