Seems like a good temporary solution however one side affect would be that the unit wouldn't stay on for the 30 odd minutes after ignition off, meaning if you are just getting out for a few minutes say at the convenience store or atm then you will need to wait for the entire unit say nav to start up again.
that seems like a fairly simple solution.
it's similar to one i did a few years ago.
i used a relay solution. im assuming the jumper setup just powers down
the radio with ignition off ?
only concern i had with this method was that the radio scans the cd trays every time it boots up.
apart from that, my mod worked until i could afford to replace the gateway.
Jason