Rotation being in: great.

Panning and rotating via fingers in the middle of everything: not so great.

Would it be possible to put invisible virtual button columns alongside the left and right edges of the screen that limit the interactivity to the camera within their space? This way when you're holding your device in landscape, you could pan left by putting one thumb on the left of the screen and right by your thumb on the right of the screen. Panning forward/back would be as simple as both thumbs on the edges pressing in the upper/lower region of the columns and rotation would be top right/bottom left for rotate left, top left/bottom right for right or however you choose to do it.

Since most sculpting takes place in the center of the screen, this would avoid accidental sculpting there with current camera controls as well as avoid resorting to visible virtual buttons and/or dedicated camera control mode.