The best defense is a good offense, and the best offense is a cannon; which you’re an expert at. You gain the following benefits.
Ability Score Increase. Increase your Strength score by 1, to a maximum of 20.
Artillery Training. You gain proficiency with Cannons.
Fast Load. You can reload Cannons as a Bonus Action instead of an action. You can use this Bonus Action only if you haven’t moved during your turn, and after you use the Bonus Action, your Speed is 0 until the end of your turn.
Starting at level 11, this doesn’t hinder your movement, and you can use one of your attacks to reload instead.
At level 20, you can ignore the Artillery property of Cannons.
Mobile Artillery. You know how to expertly handle Cannons and their ammunition; the weight of cannons and cannonballs count as half for you.
Siege. Your attacks with Cannons deal double damage against objects and structures.