There's this dual esc, commonly used for tracked models, but also work well to turn the "mix" off and use the two motor controllers seperately. I use the 2x10 to power my six drive motor adt and the other controller to power up the hyd pump... whereas you would use the 2nd esc for your screwdrive dump mechanism.
http://www.robotmarketplace.com/prod...ER2X12-RC.html
I haven't looked at this site since last winter, they now have a 2x12 dual controller, but the BEC still sucks with only 1amp supply to the rx. I've been adding the rx batt to my models for extra current draw on the rx for many servos and you're likely going to use a 1/4 scale servo or something similar to steer your adt, so this will be a necessity for more rx power.
http://www3.towerhobbies.com/cgi-bin...?&I=LXSWL3&P=M