Tank treads are expensive, add an unnecessary level of complications, could cause you to blow your main breaker, and turns are very taxing on the system and require a lot more of your battery. If you want to keep the robot level and stack the totes, just make your mechanism hold the stacks 3" from the first wheels of the robot, that simple. It's not bad to explore your options, but in this game, a simple kitbot will work much better than it would've last year. Last year custom drivetrains were really useful to withstand the beatings, avoid defense, and traverse the field quickly. This year however, you shouldn't need to build such a robust, and fast drivetrain. The kitbots offer good methods of attaching superstructures, and are a generally good option. If you want speed, you can use two CIMS with the gearboxes in the kit already, if you want control you can write code that gives you a fast and slow option. Team 1114 has a really useful and informative document about this,
Here I'd suggest reading it and seriously consider not doing tank treads.