If by the standard political/signaling rationale you are referring to the IR theory literature on costly signals (e.g., Fearon and Glaser), then I humbly suggest your language on the causal strength of withdrawing U.S. nuclear weapons from Europe is too strong.  Rather than "would go a long way," I would say "could (or might) contribute to promoting . . . ."  Frankly, we do not know what will happen as a result of withdrawing up to 240 U.S. nuclear weapons (number cited by Federation of American Scientists) from Europe.  Other countries, such as Russia, might simply say "whatever."  I am not convinced that Russia sees gravity bombs as a threat to its nuclear capabilities.

You are probably correct in suggesting that the weapons are not needed for deterrence.  The weapons are supposedly in Europe to provide our NATO allies a role in nuclear decision-making.  As many analysts have pointed out, the United States can provide nuclear capabilities from over the horizon.  Thus, I think the U.S. government should pose two simple questions to NATO governments: Do you want U.S. nuclear weapons based on your soil?  And if so, to what end?  If the answer to the first question is "no," then the United States should withdraw the weapons.  If the answer is "yes," then the United States will have to weigh the pros and cons of various force structure options in light of the answer to the second question.