I think that multiple bags is probably the answer, because no single bag can fit all situations. I have a very nice hard side case that is great for travel, holds everything and the hard sides protect it very well, but not practicle for park usage.
And my search is still going on
so far I like the cannon bag for the price, the slings look good for access, but not sure how I would like it when my back is hurting with the weight being unevenly distributed. But I will get one soon, even if it isn't the right one, it will be a starting point.