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.
Ability to steal enemy and ally magazines in their bodies
The fact to not be able to pick up magazines on dead body is kinda stupid. i'm 100% favourable to it