A very good idea

...I guess :D

For defenders/guards:
My idea is when you doubleclick a dagger while you are wearing a mace and a shield to be equipped the dagger on the one hand and on the other to be the mace without opening the inventory and putting the dagger on the shield place.

For the guards the same (as you already know most of the guards use their shields to use the stun skill only)
PS: I am not talking about the dex guards

For temps/priests:
The same too

And I am sorry if that idea was already offered.

yeees 100% agree.