Tank Commanders are in the upcoming Astra Militarum codex, and for those of us with lots of Leman Russ's, this is your chance to really bring them to the table. Earlier today (or late yesterday for some) the Black Library put the Astra Militarum codex up for pre-orders and inside it, information for Tank Commanders, including their orders.
Here is a link to the Black Library if you would like to download the sample there.
http://www.blacklibrary.com/games-workshop-digital-editions/codex-astra-militarum.html
This is what was revealed.
Any Leman Russ can be taken as the Tank Commander's vehicle and increases the BS of the tank to 4, and can be chosen to be the armies warlord. The Tank Commander's Squadron count as an HQ choice for the entire battle.
Orders
At the beginning of the shooting phase, roll a 2d6, and if the result is less than 9, choose one of the following orders to take effect.
*Full Throttle: Tank commanders unit moves flat out, moving 6+d6 even though they are heavy
*Gunners, Kill on Sight: Tank Commanders unit shoots and the Tank commander must shoot at a different target.
*Strike and Shroud: Tank Commanders unit makes a shooting attack, and then all vehicles that have not used their smoke previously must use their smoke launchers.
Personally I find these a little disappointing. The orders revealed so far only effect the Tank Commanders unit, so I hope there are more to be revealed. I can see Gunners kill on sight be effective, but I was hoping for some more flexibility with tank commanders. Of course I will wait for the codex release for final judgement but the orders at first glance are rather limiting.