Sounds like a slam dunk penalty? Cynically, and in line with Cosi's remark above, even if it's dubious I think they'll give it.
Hamilton on pole, Vettel at best 4th means that Hamilton can lead home a comfortable 1-2 for Mercedes and win the championship. F1 gets to make a big deal out of the podium, smiles all round.
If Mercedes feel they have to manipulate the result to win it, it sours F1 in the US again. A grid penalty here probably all but alleviates that risk.
Hamilton on pole, Vettel at best 4th means that Hamilton can lead home a comfortable 1-2 for Mercedes and win the championship. F1 gets to make a big deal out of the podium, smiles all round.
If Mercedes feel they have to manipulate the result to win it, it sours F1 in the US again. A grid penalty here probably all but alleviates that risk.