I think it would be interesting to be able to equip up to 3 weapons but only use 1 (2 if its duel wielding) at a time, say you equip a dagger and a sword and shield, your dagger would still be visible, so would the scabbard of the sword, but the dagger would count as your secondary weapon.
as for placement of equipment, I'm a fan of shield on your back, and the should be two scabbards for duel wielding..