battlebit has a very unique reload system such that you can perform different reloads by tapping, double-tapping and holding the R key. with this system, I think it would be possible to add a reload system for double mags
for example
tapping R once can just do a standard tactical reload
holding R can drop the mag
but the special part here is the double tap R. you can do this to swap in between the two magazines and perform the quickest reloads in the game at the expense of a very slow standard magazine reload and drop.
Devs can always add the option to swap around the binds for personal preferences
there shouldn't be any expense to this other than a slightly slower running and maybe ads speed as it's a bigger mag. but it opens to even more play styles and c'mon, it looks sick
edit: if you scroll down the thread abit, you can see mark here making a nice UI for this idea.