Be nice if you could buy a merc who comes with his own container, and will willingly use it (automatically putting carried items into it, and automatically pulling items out of it when you ask for them).

Presumably, a porter would not assist. They might even be cowardly (flee if engaged in combat; maybe run back home if injured; maybe throwing goods on the ground when running away in panic; presumably willing to wait for you someplace safe, if asked).

Be even nicer if porter "slot" was different from merc "slot".