[Vincent Rapide]

You put in the key but shift lever is stuck in PARK so you can only drag the rear wheels (aargh). Connect a 12v battery, the lightest one available - I used a small Li-Ion jumper thingy, to activate the car. Now you can turn the key ON and shift out of Park and into [D/N]. Leave it in [D/N] and disconnect your 12v source. Now you can roll or tow the car, using the handbrake as needed. The key is now captive in its slot (!!) and the shifter stuck in [D or N], but at least you can move the car easily.
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[Yinzer]

You put in the key but shift lever is stuck in PARK so you can only drag the rear wheels (aargh). Connect a 12v battery, the lightest one available - I used a small Li-Ion jumper thingy, to activate the car. Now you can turn the key ON and shift out of Park and into [D/N]. Leave it in [D/N] and disconnect your 12v source. Now you can roll or tow the car, using the handbrake as needed. The key is now captive in its slot (!!) and the shifter stuck in [D/N], but at least you can move the car easily.
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By D/N you mean either drive or neutral? I presume if the car is dead, there is no diffrence.

 

[Vincent Rapide]

Yes it is now locked in either D or N. Remember to pop it out of P before you remove the battery! I can't wait to roll it down the hill into winter storage - might be a long while before I drive her again
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[Jmk2020]

There is also another option. Similar to your but maybe more technical.
You could power the permanent 12V also via ODB connector and plug in a ELM327 dongle.
So push button to wake up the car or short switch on and off again. Send via ELM327 the right command and the lock of P is released even with failure which prevent on this in normal conditions unplug your setup and the key is yours and the car is rolling in N.
Ok without 12V battery you could only lock the door by key