I have a 2001 3.0i, and once drained my battery by leaving a GPS plugged into that 12V outlet in the passenger footwell.
And for the OP's question about whether it would work to power off and on each time, sure that would work fine. Except for the time you forget to power off and the battery drains. And then for the time you forget to turn it on and don't have the video you need. So no, you really need to get that switch thing figured out.
I know in other cars, there is sometimes a little relay at the fuse box that switches power for the switched power outlets. Then people short those out to enable power on all the time. You want the opposite, so perhaps adding a relay would do the job.
Whatever the solution is, I bet a lot of us will be interested in it.
