Hii Mitch,
You can run Unfirm heuristic which can Un firm the Firmed planned orders. But This heuristic only un firm those order which get firmed due to date fixed indicator, not others.
And we also can't un firm Out put firmed order by any heuristic. Because Out put firmed indicator is only coming when the order has been manually changed by any user.
It is also applicable for input firmed orders,Because input Firmed indicator is coming if any user manually changed any component quantity in the planned order.
So those order can only manually un firmed.
And I Guess there is no such heuristic to remove firm indicator for those firmed orders.
Regards
Debashis