As Graybeard would say, "It has all been done before." Also I still have the recommended books for wildcats on my Christmas list.
Had too much time on my hands lately and I took a long hard look at the 357 Mag "family" - 38sp, 357Mag, 360DW and 357Max, and also at the 44 Mag - 44 Special, 44 Mag and 445 Super Mag. I am sure there is something between 44Mag and 445SM, but I could not find it when I went looking.
I pondered the possibility of applying the same "family" idea to other "almost" straight walled cartridges like the 444 Marlin. (The 444 has a .015 taper). After another member offered up that the 45-70 handles short cases (1.80") without any issues, he just trims cases whose neck splits and makes them whole again, they are then short of the 45-70 min. case length spec.
I applied the 357/44 family case length differences starting with a full-size 444 Marlin and working backwards. Excuse the names but figured they would do for my own use. I came up with a 444 Special - 1.775", 444 Magnum - 1.900", 444 Magnum+ - 2.016", and the regular 444 Marlin - 2.225". That would make it even more versatile than it already is.
It does not require any rifle or reloading mods, and I like things that are different that you can get for free...Yep, too much time on my hands alright!