Years ago I did a few "kits" which were as I remember, Caywoods, and Cabin Creeks. Both taxed the beginner on basic use of hand tools. These "kits" were not guns in the white by any means. They required final lock mortise work, triggers, and guards, and pinning. Touch hole liners had to be drilled and tapped, and the stocks were roughed out and required alot of work to reach final proportions.The barrels had to be tennoned and pinned and required much draw filing....You could call these semi custom I guess.
This of course was before CNC machining. If I remember Brads kits used a collection of parts from different suppliers. The barrels were Colerain's, the locks were from Chambers, the stocks were from local Pennsylvania boys who cut to his specs. Brad did hand tune the locks, which for a beginner is good, but I believe every rifleman should be able to tune a lock and set trigger weight.
Someone mentioned the disappearing suppliers of parts and I think that hit the nail on the head. Any gun I build these days will have a Bobby Hoyt barrel. His barrels are truly custom and built one at a time which I dig. Problem is, one day he will hang it up and I don't see anyone filling that void. Sure you can go CNC but such things have no interest to me. Stan Hollenbough no longer makes locks. His shop was less than an hour from me.
I have been building self backed long bows as long if not longer than long rifles. I started about 35 years ago. I would drive out of state to seek out fine osage. The whole process of selecting trees, felling them, staving them out and curing them was a step I relished and the beginning of a process that turned standing trees into works of art that had to function under the great stress of tension and compression.
I popped in on one of these "archery" sites not long ago to see many throwing plaudits at these Asian made "bows" that can be had for less than a C note. I guess I ain't in Kansas anymore. There is time and a season for everything, but I remember the "old days". I am only 63 but I do feel like Rip Van Winkle, asking myself how did we get here. There are no power tools in my shop. I use no magnification as most of my serious work is done on an outside bench to capture the benefits of the Sun. True I am a hobbyist. I spent 33 as an Electrical Contractor working in the mid-Atlantic, so I know all to well about technology. They very last thing I want is to introduce that stuff into my art.
I am not against those who do, Lord Knows. I write this to the OP. The answer is NO!!!....So long as I can get my hands on hand made parts, I will continue to build!......Hope everyone is keeping warm!