A similar topic was discussed here not long ago, and as usual, there wasn't much agreement. Be that as it may, if you want to build such a thing, go for it! A lot of southern mountain guns use a wood screw through the tang with no problem.
As for If there were PA style long Rifles made as a barn gun ( a modern name I believe), IF, you follow a set of parameters that generally describes a long rifle, ie, say pre 1825/1830 flintlock Rifle, you won't find many made as a barn gun. It seems to me, and just my experience through the years that the basic long rifle had a cheek piece, butt plate, side plate, trigger plate, patch box and nose cap.
If you include a fowler type, basic's will be different. Different basic's also if you include later made percussion and half stock guns, rifles, smoothbores, fowlers, etc.
Just my opinion, and others opinions will vary.
John