Quick google shows Airbus/Boeing only have baro vnav
Don’t they validate baro vnav paths using sbas signal?
Load of Airbus/Boeing are not approved for LPV (GPS+SBAS only) otherwise the question of wrong QNH in L/VNAV is moot …
On A320 your whole descend trajectory will be affected due to wrong QNH setting on a non-prec app (VOR/NDB/RNP) there is no GPS altitude taken into account. We practise that on the sim sometimes.
On the other hand – the old GNS430W will protect you as it has SBAS – so your glide will be OK. You could just bust your minimums as they are based on BARO ALT.
Airbus A320 now has ALTSM which monitors QNH vs GPS altitudes during BARO VNAV…the article describes how the new Honeywell TAWS works for alerting on QNH/GPS deltas when the aircraft is outside EGPWS TCF envelope
https://safetyfirst.airbus.com/app/themes/mh_newsdesk/iframe.php?p=47599
monitors QNH vs GPS altitudes
Good to know this is on my approach checklist, since for ever 
“ Airbus A320 now has ALTSM which monitors QNH vs GPS altitudes during BARO VNAV…“
Still it has to be implemented by airlines.
At the moment it doesn’t work.
Yes it has to be adopted by the airliners but I hope it does not require recurrent “flight crew training” every 6 months
No. For sure not. Just additional safety feature. Like ROW/ROPS.
