You said you didn't understand why they wouldn't let you equip the same weapon in both slots.
So the starter weapon comes in because by making you use a second weapon, and since it's almost a given that the abilities scale of the weapon you use......
If you are using the same weapon equipped (not 2 of the same type etc, the same weapon) swapping bars is a formality, so why bother? Just give us 12 slots, 10 regular, 2 ultimate, and let us fill them up with whatever we want. Sword based abilities would use the equipped sword for damage, etc.If you only had bow abilities slotted, then they would just scale off the bow you had equipped.