The way to do this is to make guns spawn at a realistic rate. The current system spawns them at a low rate that works only because there are just a couple handful of guns, however the guns we do have lose condition far too quickly.
The most common complaint from anti-gun players is that making guns less rare makes the game too easy and that is actually somewhat of a valid complaint. Having a wider selection that introduces incompatibilities kills 2 birds with 1 stone; keeps both camps happy. You get more guns spawning at a realistic rate, but introduce enough complexity that makes it less straightforward than, for example, simply having one magazine to worry about per caliber.
I believe this would be no more demanding than the crafting and recipe system already is. We often need very specific items and tools to satisfy a recipe. I don't see why guns, magazines and ammo should be any different.
Currently, inventory transfer goes from the smallest items to the largest. This seems strange, as it means the player will need to explicitly grab certain large items manually if they're on a time crunch, as well as leading to storage containers being less optimally filled, as tiny items will flood the container first, reaching thresholds that will prevent the larger items from fitting anymore.
Either have an option in the player's config, or even some way of doing so in the inventory panels themselves would be appreciated.
Can you try increasing the RAM assigned to the game?
Open the game install folder (Right click the game in steam > Manage > Browse Local Files)
Find the ProjectZomboid64 json file and open it in a text editor.
Find the line "-Xmx3072m" and change it to "-Xmx5G" and see if that helps?