I've been looking through the forum and there seems to be no commando specific PvP build. So here's mine, feel free to give me feedbacks and suggestions.
1) Nova Blast + Plat Shield
2) Full custom Titan set
3) Plat dodge implant
The thing about this build is that you gonna have loads of money. LOADS. With nova currently going at 100k and full titan going at around the same price, its 200k credit plus 30 plat for the shield and implant. With the update coming, if you currently do not own any of the above, I suggest that you don't try this unless you got plenty of credit and plat to burn.
This build is not about tanking or holding aggro, it is a pure PvP build, so it will not perform well fighting mobs or being a tank. Growing rage is great in PvP. Graviton slam have decent damage and slows opponent, great for slowing opponents that like to run around all day. Singularity and neutron stomp are essential for doing the backbreaker combo. You could use singularity and BB, and almost immediately you could do the neutron stomp and BB combo. This is effective except when the opponent dodge either one of the attack, which renders the entire combo useless.
This build is about balancing between attack skills and self buffs. Increase mass is great as the +300 armour gives comm the extra ability to tank alot of damage. The armour given above also have 32 dodge, which makes this build very difficult to kill. The only thing i am not sure about this build is vigor, since i have yet to test it in PvP. Im not sure if it heals well since eng heals are cut to a fraction in PvP. This skill is great for healing during battles. However, if you are against running and hiding during PvP to heal (which I find it alright), you may place all 4 points into Neutron stomp for additional damage. Otherwise, run around/away/in circles to heal when you have low health before engaging the opponent again. Also, you could run to delay time when your opponent is high on buffs, and only attack when their buffs end.
This is the best build i could think of right now. Most of it came from observation and testing. Hope this helps!