The self disembarking/timed disembarking problem could easily be solved by having two exit points - this is done when the ship is in port.
The self disembarking exit would go straight to customs bypassing the baggage hall, which would have the added benefit of delaying queue jumpers, whilst the timed disembarkation would be as normal. The two could then quite easily operate side by side.
I do think though that at some point in the future self disembarkation will be stopped and all luggage will go into the baggage hall and anyone trying to disembark with cases will have to wait until the end. The reason why I think that this could happen is that more passengers appear to be wanting to self disembark with the result that the ship becomes gridlocked with passengers and cases everywhere.
To be honest I have never understood the need to rush to get off the ship at the earliest opportunity rather than in a calm orderly manner.