Presuming that you are on a domestic (or pre-clearance) diversion and that you are on a gate as opposed to being refueled somewhere off a gate, there is absolutely no reason you can't separate voluntarily at a diversion point.
Te carrier is not required to forward your luggage if you have checked luggage, so don't expect what happened in
#14 to occur on your flight.
It is b.s. that a carrier can't permit you to offload because it does not publish the route.
It is b.s. that you can't voluntarily separate from checked luggage (noting the domestic issue above).
Weight and balance will need to be calculated after refueling, so best to offload ASAP as the crew timeout issue may come into play if you do it after the aircraft is refueld and w&b has been rerun (as it will need to be recalculated if you do so).
International arrivals are a different issue and require CBP presence & permission.