I initially put a long XS LeverRail on my JM 1894CSS, but the carbine had an out of spec rear sight dovetail (among other issues) and the combination was a bit of a botch job. In the end, I sawed off the front of the LeverRail at the point where I did not lose any useful - to me - scope ring real estate, and I have never missed the extra length. So no, a long rail is not necessary for me either, though I like the semi-integral rear aperture. Threaded barrel? Meh. They could add that feature and I'd just leave a thread protector on.
Were I a younger cat, I would pull a Diogenes and search for the gunsmith who could cut the barrel/mag tube down to just over 16" and remount the front sight just behind the barrel band... and do it without screwing things up, thus tanking the carbine. If he's around here, he's in hiding. To be honest, what it would cost would probably not be paid for by being a whole lot handier than it already is. But I have it in my head that I want a 16" (or so) 1894 CSS.