The Commander Class isn’t exactly a new class but just a conversion of the Wizard Class into something less magical and more military.
Did you said Burning Hands or was it Flamethrower Unit?
It works as if you had a whole army surrounding you, but you’re actually the only target your enemy is aiming for. A Commander uses Tactics, instead of Spells, and hence the flavour text for any of those spells must be rewritten. As an example: instead of burning hands, a soldier unit with a flamethrower appears right in front of you and projects a huge fire wave. Specifics like damage, distance, area of effect, are exactly the same. I know, I know, what about the soldier unit with the flamethrower? Where did it go? After the Commander spent that action, it disappeared. Oh, well, this is a Fantasy Setting, where you can imagine just about anything.
Imagine, for instance, that this Commander is followed by an army of specialized troops, which come and go and perform an array of incredible deeds, all related to the military. Your enemies aim at you and not your soldiers, cause once the Commander is killed, your army is defeated.
Instead of an Spellbook, the Commander uses the Manual of the Tactician. Rules designed for including more tactics to the manual work the same way as for spells with the Wizard’s book. Just that gold doesn’t go into components, or a very special kind of ink, but to pay the soldiers for their services. The Commander prepares a limited number of Tactics after every long rest, which adds to the flavour of being of high military rank. Instead of studying and memorizing a Spellbook, imagine yourself giving orders to your officers, and those are the plans that will be ready for next day.
A Commander uses Charisma as his primary ability score. The Tactic save DC equals 8 + proficiency bonus + CHA modifier. The Tactic attack modifier is equal to the proficiency bonus + CHA modifier.
I will add some flavour text for a set number of spells having in mind a character designed by myself, called Mortajo. A version of Mad Max’s Fury Road fictional character Immortan Joe. The flavour text may vary depending on the character and background. Same exact tactics (spells) may have totally diferent flavour text depending on the world setting you are playing on, or the type of army you would like to command.
SET OF MINOR TACTICS KNOWN BY MORTAJO (Minor Tactics work like Cantrips)
Thunderpoon Unit (fire bolt): a slave soldier launches himself at a maximum distance of 120 feet and attacks with his explosive thunderpoon weapon, dealing on a hit 1d10 fire damage. The Commander must make a tactic attack against the target. This symbolizes having given the right directions to his soldier.
Other Minor Tactics: Repair Unit (mending), Slave Messenger (message).
SET OF FIRST LEVEL TACTICS
Flamethrower Unit (burning hands): a slave soldier with a flamethrower appears right in front of you and projects a huge fire wave. Any creature in a 15-foot cone must make a DEX saving throw. A creature takes 3d6 fire damage on a failed save, or half as much damage on a successful one. For every higher level slot you spend to use this tactic, add another 1d6 to the damage roll.
Other First Level Tactics: Pole Unit (jump), Motorbike Unit (longstrider), Slave Servant (Tenser’s floating disk), Slave Bodyguard (shield), Quiet Maid (unseen servant), Watcher (alarm).
SET OF SECOND LEVEL TACTICS
Bullet Burst (cloud of daggers): you command one of your soldiers to fire his machine gun into a cube 5 feet on each side, centered on a point you choose within range (60 feet). Any creature takes 4d4 piercing damage when it enters the area. For each higher level slot spent on this Tactic you add 2d4 to the damage roll.
Other Second Level Tactics: Retreat Command (expeditious retreat).
SET OF THIRD LEVEL TACTICS
Maidens Sanctum (gentle repose), Hostage (hold person).