Notwithstanding the asymmetic considerations, how about this: the LE flap will move the CoP forward and the TE flaps move it back, the two working together ensuring that the CoP doesn't move too far (back). If the TE flaps aren't fully extended and the LE flaps are extended beyond 15deg, the resulting balance of forces of would be outside certification limits. Practically speaking, could an otherwise legally loaded a/c suffer loss of authority in pitch in these circumstances?
tW