It'd be neat if a remove/discard/reload took less time than a remove/retain/reload operation, and you could choose between the two.
And if empty magazines were somehow a desirable asset. You could shuffle ammo from two half-empty mags into one full one, or ammo was found only in raw cartridge format and stuffing mags required a deliberate keystroke and a progress bar. Discarded mags get destroyed, but you could find new magazines once in a while.