"While they can be fired un-set, the resistence and feel are horrible"...the same can be said for double-action double set triggers!!! The angle of the trigger bar is HORRIBLE, and the sear has to drive itself up the ramp-like sear bar, making a long, heavy, and disconcerting sliding feel. I made a set trigger once with a VERY tall front blade with an angle more like is on a normal single trigger. Much better and lighter, but the pivot point is so low, the sear slides across the bar a good distance and is not the most pleasant trigger I ever pulled! But, once again, much better than the normal type.
When shooting a gun with set triggers, I NEVER fire them unset, so could easily do well with "single-action" set triggers, as many, and likely most, old set triggers were.
There are PLENTY of York county rifles with regular double triggers. Find, if you can, the little book "Gunsmiths of York County, Pennsylvania" by J.B. Whisker. There are several late Axariah Alloway rifles with sets, and a NICE Georg Eyster with sets. A Martin Fry, an Andrew Kopp (very possibly made in Maryland), a John Shriver, and a George Shroyer, all with double set triggers. There are more in "Thoughts on the Kentucky Rifle in its Golden Age" by Kindig, including the justly famous "George Nunnamacher" rifle.