From a narrative/setting I would like this, from a gameplay hell no. Old timey guns are so plodding and clunky.
Old timey? What the heck do you think they used in WWI? It's not the bloody revolutionary war lol.
WWI had Shotguns, SMG's, MG's, sniper rifles, semi and full auto rifles, melee weapons (everything from bloody maces, knives, to shovels were used), to artillery, horses, tanks, and airplanes.
Basically almost everything you can get in WWII in terms of gameplay, you can get in some form in WWI.
Also for those who might not know much about WWI, it wasn't simply a bunch of trench warfare. Trench warfare was a western front thing, the entire eastern front never devolved into that kind of fighting.
You had fighting in many varied environments, from deserts, to forest, to ice and snowy mountains (Where avalanches caused a whole mess of things, still to this day the most number of people lost to avalanches during war is WWI).