Your Panasonic TV might have commands in a third device number that you don't know about. I don't know a practical way to find out.

My Orion VCR is NEC2:128.123. I asked around for discrete on/off but no one knew them. I'm pretty sure there aren't any. I think it's VERY unlikely that it uses a different device code. (Someone did tell me the eject code that wasn't on my original remote).

My Orion VCR has some very annoying "blind spots", periods of time after it gets some fairly simple commands in which it is blind to incomming IR. I haven't tested, but I'd be surprised if the blind spots are the same when it's off. It would take some experimination (and knowing how to contruct commands back to back with controlled small delay between, less than a macro might use), but I'm fairly sure there is some innocuous command you could send before a power toggle that would make the VCR blind to the power toggle when on but not so when off.