A short suggestion - if you have two mags of the same type and some duct tape, you should be able to attach the two mags together, to decrease reloading time, and save space and organize your inventory a bit better, maybe at the cost of your gun weighing a lot more, perhaps taped mags on a gun would way a bit more than the mags together in your inventory.
If inventory space is going to be more of an issue in UII (for example, less space in clothes and the inability to carry specific items in certain places) then this could prove very useful, somewhat similar to the idea I have seen brought up many times or pouches for extra rounds on shotguns to save loading time and add more storage space (two mags together would take up 1 slot).
This is a very common thing to do in the real world, and I think it could also be cool and useful as well in a survival game like UII. Having two mags attached together could make reloading faster, for instance if you have the mags on your body, it would take a lot slower than having the mags taped together- if you run out of ammo in the one mag, you hit reload and it will remove the mag and put another instantly (although the empty mag is still attached).
Perhaps taping together the mags would require a special skill branch, for instance when you upgrade it it lets you tape 2 mags together, then three mags together.