Shot shell pants might make sense on cold days with sporadic rain or snow, but the idea of softshell shorts seems odd to me. Short shells were developed to be breathable and good for light rain or snow. I think they are great for single-purpose use for a day hike, skiing, or commuting, but they are heavy (not to mention expensive) and don't fit into an ultralight pallet of clothing.
If it's hot (like August), running shorts are light and easy to come by. I use some Nike shorts with a soft polyester built-in brief. From there the choices run the gamut from short inseam to long, built-in briefs or none (some briefs chafe on long distances), and ultralight materials to heavy cotton canvas.
I've found so many shorts in thrift stores that I don't bother looking in retail stores. You can buy just about any brand for $2-$5 a pair. I have Ex Officio, REI, Patagonia, Gramicci, and Nike's that all came from thifts. My whole collection doesn't equal the cost of a new pair from REI!
In general, I like zip-off pants for one-garment versatility. Mountain Hardwear Pack Pants are very good, but on the heavy side and retail is (gulp) $100 a pair. REI Sahara pants are a good lightweight version. Ex Officio Bug Off pants are pre-treated with permethrin if you hike in buggy areas (or you can treat other choices yourself). Columbia makes several models. The "GRT" line is heavier but more durable and might be better for colder weather.
I'd like to see a pair of light quick drying nylon hiking pants with tabs and buttons (like some shirts sleeves are done) so you can roll the bottoms up to just below the knees. That would give good cooling and on-the-fly adjustability on the trail without fiddling with zippers and losing the zip off sections. Some sort of drawstring or other bottom closure should be standard on any hiking pants.