jmmilner
Only the TCAS scenario really works in my mind, and only if ATC has already established a context in which the false warning would make sense to the pilot.
Speaking as someone who has successfully spoofed TCAS (all legal and above board in a controlled trial) it is not that easy.
TCAS uses reported altitude and rate of closing range. You can spoof one but not the other. If you can get the victim aeroplane fast enough and low enough you can spoof an alert with a ground based transmitter (directly beneath the track). But only briefly. As the range gets really short the alert cancels as it looks like the 'threat' is passing safely to the side.
TCAS has built in protections against providing RA's to fly you into the ground.