Here are the advanced classes for all of the imperial classes:
Bounty Hunter
-Powertech
Flamethrower
Defense / Energy Shields
Tank
-Mercenary
Dual Wield Guns
Missiles
Ranged DPS
Sith Warrior
-Sith Juggernaut
Single Saber / Heavy Armor
Fear and Darkside Auras
Tank
-Sith Marauder
Dual Wield Sabers / Armor
Saber fighting specialist
Melee DPS
Imperial Agent
-Operative
Blaster Rifle / Energy Blade
Stealth
Burst Ranged damage
-Sniper
Sniper Rifle
Cover, Ambush, Orbital Strikes
Ranged DPS
Sith Inquisitor
-Sith Sorcerer
Single Saber
Force Lightning / Force Drain
Ranged DPS or Healer
-Sith Assassin
Double Bladed Saber
Stealth
Burst Melee DPS