So Armored Core 6's chapter 1 boss is a pretty big hurdle if you haven't internalized the lessons the first mission's boss was trying to teach you. I've seen some designs that offer easy solutions to it, but I made my own based on the style of game plan that got me through the end of the game. Everything in this build is available in Chapter 1 (without log hunting), and I reset my OST chip build and only spent the 6 chips available at that time before doing the fight with this build.
Here's my first try with it, which turned out to be an A rank despite some really sloppy Boost gauge management that got me hit by one of Balteus's most dangerous attacks twice. Forgive the video quality, I'm not a Content Creator, my recording setup is ancient and suboptimal.
BATTLE STRATEGY:
This AC should fair just fine against both Sulla and the two encounters beforehand. If you're struggling, you can drop down into the water and flank the laser cannons in the beginning. If you're not used to using Assault Boost a bunch yet, both the encounters with the laser cannons are great scenarios to practice using it. Against Sulla, get up in his face when your weapons are off cooldown and be relentless. Back off a little bit otherwise. Try to only fire your shotgun when Sulla is unlikely to move again - i.e. immediately after he lands or decelerates from a quick boost, but don't sweat it if you whiff it. You can use the missiles to apply pressure while you wait for an opening. Against Sulla, you want to punish staggering him with the Pulse Blade, which is your best offensive option. Point-blank missiles are good for this, too.
Balteus wants you to be far away from it, so don't be. Assault Boost, Assault Boost, Assault Boost! So long as you get right on top of Balteus, you probably won't have to worry about its missiles. Armored Core isn't Dark Souls, you're gonna take some chip damage, don't sweat it. During an Assault Boost, remember you can pull left or right on the analog stick to dodge without losing (much) speed - this is most useful for dodging Balteus's cannon shots - the one you get the audio warning for.
Balteus's biggest hassle is its pulse shield. Incidentally, pulse shields are pretty dramatically weak to the pulse blade you start the game with. So when you approach with Assault Boost, fire off your shotgun and/or missiles, then terminate the Assault Boost with the pulse blade. So long as Balteus stays nearby, follow up with weapons as they come off cooldown. If Balteus runs from you, pursue with Assault Boost. If Balteus does a maneuver that means your Assault Boost is no longer a straight line, pull back on the analog stick to cancel it, let yourself touch the ground long enough to recharge your boost gauge, start a new Assault Boost. The OST chip loadout I used gets you one Assault Armor. When Balteus's shield is down but his stagger bar is no longer flashing, you can use it to instantly stagger him once. Keep in mind that the start-up time is pretty long, so you might not get a good opportunity to use it. At around 50% HP, Balteus will Assault Armor you, so be sure to back off when he's in that range (Ayre also has a voice line that indicates it's about to happen). As for the fire slashes... eh, kind of don't worry about them. They're a punishment for trying to fight him at mid-range, and you won't be doing that.
