I doubt it would be very useful for that anyway since the chance of getting two of the same weapon with different prefixes is pretty high.
Seems like the main thing this is intended for is extremely long-running mob farms, since chests will be able to suck up items when activated. Weapon stacking means if you have a bunch of chests, they won't get filled up just with duplicates of the same weapon.
I think weapon stacking looks ugly and feels weird, but I can't really imagine any other arguments against it.