Switch Primary & Secondary/Side Weapons In Combat Seamlessly

I would like the ability to switch to a secondary weapon when I am in combat. The ability to switch to a hand gun seamlessly as a secondary/side weapon without having to go into the menu and unequip then equip another weapon as it takes too much time.

I am not asking to switch between rifles and assault rifles or any other big weapons but to be able to switch between an assault rifle/rifle and have a slot available like close combat and melee weapons that is reserved and can hold a hand gun for seamless switch in combat would be perfect. I believe this would make for a better experience when in combat, especially when you are playing on the harder difficulty levels and caught up in trouble.