They won't fit on a single FH. Maybe you could do it on the inaugural launch of the FXXXX Heavy, with tight margins.
The heat pulse will be short lived, can you imagine CO2 emissions, it may just trigger a Venus style runaway greenhouse!
My point was that they can be and it is not that big of deal and precedence had been set. Nobody would be fire and there would be no incompetence.
Falcon 1 never had a dummy payload; the closest was Demosat on the second flight
Delta IV Heavy was the only recent rocket that I'm aware of that flew first with a dummy payload (and good thing too, considering it failed to reach orbit).