I figured out, the mouse pan mode is working pretty nicely with my TrackIR 4 Pro (+TrackIR 5 final B driver) mouse emulation.
New Controls:
F1 = internal view mode.
F2 = external view mode.
F3 = Snap pan mode with numpad-keys.
F4 = Mouse pan mode.
F11 = Reset mouse view to forward. This works nicely, if your TIR reset is on F12-key.
Mouse wheel up/down = zoom in/out in ext. view mode