I hear you... It would be nice, but I think mare's legs have a very limited market in the US. Even here, a lot of people don't find them to be of any use. I'm not one of them, we sleep with a .44 mag rossi ranch hand at our heads in the tent, and it's full of 310 grain hard casts ready to leave the barrel at 1,450fps. It may not be the most practical gun but with the hollowed-out butt stock it weighs just over 4 pounds and it's 2 feet long. Much easier to pack around the mountains and manipulate in a tent than even my guide gun.
I think right now your best bet would be cutting down the stock on a Chiappa with 12" barrel. They are just under 31 inches long, so you could lop 4" off the stock, install a new butt pad if you like and have a 26.5" rifle with a very short LOP. You're talking about 2.5 inches longer than a mare's leg. I would also hollow out the stock with a large drill bit to further reduce the weight. Still, it's a big ol' heavy rifle action and the octagon barrel is of no help in keeping the weight down.
Since we're talking wishful thinking, what I would like is if Rossi made a stainless ranch hand in .454 casull. Everything is already in place for such a firearm to be produced, except demand... The pistol cartridge would be less affected by a short barrel and likely come out ahead of a .45-70 at equal length. I had a Rossi trapper in .454 with a 16" barrel, and it would send off 300 grain factory jacketed rounds at almost 2,100fps. Matched my .45-70 guide gun with a 2.5" shorter barrel and 1.5 pounds less. Sadly, it had to go back due to excessive head space and horrible finishing of the receiver.
Hope springs eternal.