Originally Posted by Chi

If you can engineer a mechanism that will pull both brakes at once, you can, I guess. The Campagnolo differential brake design might work nicely here. But again, without individual control of both wheels, it would be hard to control the bicycle, I think. I can see situations where only one wheel need braking, esp. in mountain biking.

If they were hydraulic disc brakes I'm sure you can build a distribution valve that will allow pressure to both calipers.