If on an xONEx you nest another r/t itin on a non-OW airline, what happens if you misconnect and miss your xONEx segment?

Considering an AKL//PPT nested ticket on NZ with onward QF segment for AKL-ZQN. The problem is, if the NZ flight PPT-AKL is running late, I probably wouldn't find out until about 2am at PPT airport. It might be a little late to make a change to the xONEx. Or, let's say the delay is on the tarmac, so no chance to call anyone to make a change.

First of all, if I misconnect I've flat out missed the flight. On normal (non-RTW) tickets if you miss a segment it is common for the airline to just cancel all the remainder of the ticket. This wouldn't happen on an RTW ticket, right? Or, even if not cancelled, I wouldn't loose my remaining bookings and have to re-book (and risk no A-bucket or D-bucket availability), right?

I figure the two options I would have is to re-book on the next day's AKL-ZQN (it's only offered 1x day). Or, if I don't want to wait, I would seek to have AKL-ZQN re-booked as a surface segment and just buy a o/w NZ AKL-ZQN ticket out of pocket and pickup the xONEx in ZQN.

So...
1. Are there technical or logistical problems with trying to make changes to a segment after the segment has flown?
2. Is there a fee? The AA rules linked to on the sticky found here does not say anything. But, the CX rules linked to on the sticky found here mention "Changes After Departure... Permitted without charge but if no show, rebooking at a charge USD125." So is AA or CX right?