Latching Changeover Relay

Hi, I am trying to figure out how to create a latching changeover circuit to allow a car stereo to be switched on via a momentary push button, as well as behaving normally from the ignition key. Normal everyday operation with the ignition key should not be affected. When parked up with the ignition key off, the momentary push-button would be pressed to switch on the stereo (latched). Then when the ignition is turned on this should unlatch the circuit and continue to power the stereo as normal. When the ignition key is then turned off, the stereo should also power off as normal. Using https://www.the12volt.com/relays/relaydiagram66.html as a starting point, I have come up with this: Would this work? Can anyone see any problems with this setup? To make this a perfect solution, how could this be changed to allow a second press of the momentary push-button to also unlatch the circuit and power off the stereo? Thanks in advance!

This is for a VW Transporter 2014 but that shouldn't make any difference in this case. 12V supply and push-button will be fed from a leisure battery.