I don't think that can be a issue of some sort, we already can steal the magazines on other weapons on the ground, what about steal theirs magazines in their pouches?
For balance, maybe add a really long action time to search it.
Its make no sense to steal weapons on the ground if we cant also steal their mags.

The fact to not be able to pick up magazines on dead body is kinda stupid. i'm 100% favourable to it

it's so commonplace that I do not understand why we can not do it.

ShowBox Tutuapp Mobdro

If you are talking about caches magazines, then they are taken from corpses automatically. After searching the corpse, pay attention to the map of the zone, there will appear the mark of the caches, if the dead found a magazine.