I cast my vote with both Keith and CH.
I have worn 18th century garb in the woods for weeks on end and it can not be beaten for comfort and ruggedness in a forest environment. it is not so much the trousers themselves that are superior, but the leggings that cover them. The leggings slip on over the pants and are made from heavy canvas, often painted, or lightweight leather. It resists thorns and brambles better than anything made today.
http://tippycurtisknives.com/aboutme.html
However it is not suitable for "blending in" during any normal activity.
CH is also correct in his recommendation. I wear bibs often and they are not unusual wear in my area. Every farmer in the region wears them. I have several pair on the shelf.
They are lose fitting and comfortable. They have numerous pockets and feature several compartments in the bib area that are very handy. Pencil slots, pocket knife slot, zipper closed pocket, open top pocket. The normal pockets are deep and roomy and will carry a lot of essentials. The straps also take the weight off the belt area. In fact, they eliminate the belt loops entirely.
Now none of these items may be what you are looking for, since you are wanting to find bullet-proof pants that shed water, resist thorns and hold up to rough wear while looking snappy with a sport coat.
I suggest you google Deluth Traders "fire hose" line. They are incredibly expensive but appeal to the yuppie construction worker that wants to look good while hauling bricks and mixing concrete.
I forgot to grab a link, I will post it below since we do not have an edit feature on this board.