1. Strongest armor you got. Front line taking most damage risk. Also feeds into natural abilities.
2. Shotgun and pistol- the only class in game that might use it (for sure on spec up Enemy Within missions) as you can use double shot with pistols. If using mod to move arc thrower to pistol, I'd do it here as well...
3. Arc thrower on assault makes most sense (closest to enemies) and can/will be used to repair MEC's. If you have it on pistol slot take a medkit with you.
4. Chitin Plating synergy with assault build and abilities cannot be ignored. Must have.