One-man Army

The Mercenary marched from the Commander's tent toward the front line with a dismissive glance at the divided Cavalry, Archers, and Infantry.  His Shield bumped solidly against his back on its sling, his Heavy Crossbow thrummed menacingly, and the unusual details of the Sword hilt at his hip drew all eyes until he stopped beside his mechanical Griffon.  "Alright Zephyr, let's show 'em how it's done" he muttered, just before the enemy's horn and drum signaled the charge.  With a thump and a crackle, two Bolts arced across the field and two soldiers toppled.  Two more thumps, and two more soldiers fell.  The Mercenary chuckled, and with practiced ease, dropped his shoulder to slide his Shield into place as he slung his Crossbow and drew his Sword.  "Now for the fun part" he said as he rushed into battle with his Steel Defender at his side and Dragon's fire coursing from his blade.

You've trained to stop the advancing enemy at any range, changing between Ranged and Melee weapons as needed. You gain +1 to Attack rolls with Heavy Ranged weapons and +1 to Attack rolls with one-handed Melee weapons while wielding a Shield.  In addition, you can don a Shield as a Bonus Action while retaining your Ranged weapon.

This feat replaces one Fighting Style you would normally gain from a class feature.