HUDs are pretty darn cheap.
I have a "HUD" alarm clock that cost $15, works perfectly and projects the time. I know the automotive side is a bit more expensive then that as projecting onto a windshield is a bit tougher, but at the same time an instrument cluster is really not that expensive at all.
I'm not worried about things like speed on the top left central display. I'm worried about the very real possibility of the central display freezing/crashing because it's doubling and simultaneously running as GPS, infotainment, and probably will hold third party apps as well. Something that is system critical that can also run user-loaded software is bad, bad, bad even if the software is Tesla-approved.
Relying on audio cues alone for important things like autopilot being turned off and speed limits is also very bad. Very easy to miss audio cues especially if music is involved or other people are talking.
If there's no HUD option or driver panel option, this can potentially be my only dealbreaker.