If yall could have one ACW weapon to "modernize" what would it be? Mine would be the LeMat Revolver in .44 Magnum with a .410 chambered in 3" barrel underneath
I would bet a lot of good money that any of the Italian manufacturers would totally balk at that because it would entail an entirely new gun while trying to make it "look" like an ACW era LeMat. Conversion cylinders are available for low power loads in .45 Colt (1860 Army/1848 Dragoon/1847 Walker) but those are not even close to .44 Mag pressures. The .410 barrel (acting as the cylinder "pin") is smaller than the original barrel (~19 gauge) so there is probably enough metal there to do that with 2.5" shells. This all assumes top of the line metallurgical steels to be used in construction, and I highly doubt the Italians would do this.
If anyone would attempt to produce one, I would bet that the price point would be no less than $2500 and probably much more, and only if there was a market for it.
In the last few years I have repeatedly tried to contact and convince Pietta to create a .36 caliber J.H. Dance and Brothers revolver, as opposed to the .44 caliber Dance they now produce. Their Dance is based upon a lowered 1851 Navy frame and a cylinder that is larger in diameter than a .36 cylinder.
To create one, all they have to do is mill the recoil shields from the standard 1851 Navy frame before case colors are applied. Very easy, very cheap. Their reply was that their marketing folks did not think they would sell.