i've seem suitcase genny+ tyrewarmer packages for less than £200.
Losing the front (or rear) on cold tyres just once will cost at least that. (and I should know!)
One sighting lap plus a warm-up lap doesn't get enough heat up, especially on a short circuit.
Allow tyrewarmers, then people can make their own choice, but I personally would be a bit hacked off if I were taken out on the first lap by someone with cold tyres...........
Cheers, Paul