Defensive Great Weapon Master

You master fighting with a Two Handed Weapon and a Shield, utilising the strap on your shield to quickly deploy it over your shoulder for defence or to return it to its stowed position on your back.

This grants you the following benefits: 

• Increase your Strength, Dexterity, or Constitution score by 1, to a maximum of 20.
• You can use a two handed weapon even when you have a shield equipped.
• You gain the ability to draw or stow an equipped shield as a free object interaction in combat.
• You can draw or stow both a shield and a weapon when you would normally be able to draw or stow only one.

Idea based on a video from Shadiversity on Youtube: "Shadiversity: Using Two-Handed Weapons and Shields together?" - youtube.com / watch?v=ttJ8LdOQdSc