Last night I put in stylus control for the car. I was going to rely on joypad control for steering so as to free up the stylus for aiming weaponry. After testing I've decided that stylus control for steering is needed at least as an option. Devices and weapons are going to be activated by icons along the bottom of the screen. I'm going to add a steering wheel icon that when activated switches control to steering. However, when other devices or weapons are selected, the only way to steer will be using the joypad. This will give an easy control method for novice players, but only by learning to use the joypad for steering and the stylus for aiming will you be able to maneouvre and fight at the same time.
I'll post some screenshots of the randomly generated maps here soon.