So it looks like you will get additional abilities within Frontier Defense called "Aegis Ranks". I just unlocked the first upgrade for Scorch called "Double Threat" which allows me to fire two Thermite Grenades before reloading. I'm gonna start this thread and fill in what all the upgrades are when I get the chance. ION Spoiler Split Shot Power (Unlocks at Aegis Rank 2) Split shots deal more damage. Chassis Upgrade (Unlocks at Aegis Rank 5) Ion's health is increased. Energy Storage (Unlocks at Aegis Rank 8) Ion's max energy is increased. Split Shot Efficiency (Unlocks at Aegis Rank 11) Split shot requires less energy. Shield Upgrade (Unlocks at Aegis Rank 14) Ion's max shield is increased. Energy Regen (Unlocks at Aegis Rank 17) Ion regenerates Energy 25% faster. Reflex Cannon (Unlocks at Aegis Rank 20) Kills extend the duration of the Laser Cannon. SCORCH Spoiler Double Threat (Unlocks at Aegis Rank 2) Thermite Launcher now fires two shots before needing to reload. Chassis Upgrade (Unlocks at Aegis Rank 5) Scorch's health is increased. Hot Streak (Unlocks at Aegis Rank 8) Thermite damage builds up a Core Meter multiplier. Roaring Flames (Unlocks at Aegis Rank 11) Thermite damage is increased. Shield Upgrade (Unlocks at Aegis Rank 14) Scorch's max shield is increased. Triple Threat (Unlocks at Aegis Rank 17) Thermite Launcher now fires three shots before needing to reload. Explosive Barrels (Unlocks at Aegis Rank 20) Igniting an Incendiary trap now triggers an initial explosion. NORTHSTAR Spoiler Explosive Traps (Unlocks at Aegis Rank 2) Tether traps explode when they break. Chassis Upgrade (Unlocks at Aegis Rank 5) Northstar's health is increased. Plasma Railgun: Quick Charge (Unlocks at Aegis Rank 8) Plasma Railgun charges faster. Trap Mastery (Unlocks at Aegis Rank 11) Northstar has two charges of Tether traps. Shield Upgrade (Unlocks at Aegis Rank 14) Northstar's max shield is increased. Plasma Railgun: Critical Hit (Unlocks at Aegis Rank 17) Plasma Railgun critical hits deal increased damage. Twin Cluster (Unlocks at Aegis Rank 20) Cluster Missile now fires two missiles. RONIN Spoiler Sword Mastery (Unlocks at Aegis Rank 2) Melee attacks deal more damage. Chassis Upgrade (Unlocks at Aegis Rank 5) Ronin's health is increased. Ghost in the Machine (Unlocks at Aegis Rank 8) Phase Dash has two charges. Kinetic Transfer (Unlocks at Aegis Rank 11) Incoming blocked damage charges Sword Core. Shield Upgrade (Unlocks at Aegis Rank 14) Ronin's max shield is increased. Wraith (Unlocks at Aegis Rank 17) Phase Dash travels further. Blademaster (Unlocks at Aegis Rank 20) Sword Core attacks generate Shield. Sword Core's duration is doubled. TONE Spoiler 40mm: Splasher Rounds (Unlocks at Aegis Rank 2) 40mm rounds deal damage over a larger area. Chassis Upgrade (Unlocks at Aegis Rank 5) Tone's health is increased. Sonar Weak Points (Unlocks at Aegis Rank 8) Enemies take 25% increased damage while revealed by Sonar Pulse. 40mm: Extended Ammo (Unlocks at Aegis Rank 11) 40mm ammo capacity is doubled. Shield Upgrade (Unlocks at Aegis Rank 14) Tone's max shield is increased. Signal Strength (Unlocks at Aegis Rank 17) Sonar Pulse's duration is increased by 60%. Salvo Core Barrage (Unlocks at Aegis Rank 20) Salvo Core fires more missiles. LEGION Spoiler Piercing Rounds (Unlocks at Aegis Rank 2) Predator Cannon rounds pierce through enemies. Chassis Upgrade (Unlocks at Aegis Rank 5) Legion's health is increased. Executioner (Unlocks at Aegis Rank 8) Close range Power Shot bypasses Doomed State. Redirect (Unlocks at Aegis Rank 11) Damage absorbed by Gun Shield recharges your Titan's shield. Shield Upgrade (Unlocks at Aegis Rank 14) Legion's max shield is increased. Drill Shot (Unlocks at Aegis Rank 17) Long range Power Shot deals more damage each time it pierces an enemy. Dreadnought (Unlocks at Aegis Rank 20) Legion is equipped with all of his kits. MONARCH Spoiler Energized Smoke (Unlocks at Aegis Rank 2) Monarchs' Electric Smoke gives her shield. Chassis Upgrade (Unlocks at Aegis Rank 5) Monarch's health is increased. XO-16: Sniper Configuration (Unlocks at Aegis Rank 8) Reduces spread and enables toggle-zoom on the XO-16. Energized Smoke Lvl 2 (Unlocks at Aegis Rank 11) Monarch's Electric Smoke gives friendly Titans Shield. Shield Upgrade (Unlocks at Aegis Rank 14) Monarch's shield is increased. XO-16: Critical Hit (Unlocks at Aegis Rank 17) XO-16 deals additional damage against weak points. Apex Titan (Unlocks at Aegis Rank 20) Monarch starts with a random tier 1 Core Upgrade.
So apparently you can check these if you click on them before searching for Frontier Defense. However, I updated the original post with all the upgrades and what Aegis rank you need to achieve to unlock it.