I wrote:
We shouldn't guess anything. There might be package clashes, it is not possible to exclude this possibility. While think about this issue I still think that we need, additionally to your patch, to handle mhchem the same was as esint and amsmath. Take for example the attached LyX file and open it in LyX 2.0svn where you have applied your patch. When you compile it, you get errors, that \cf is already defined. The user has no choice to deactivate mhchem but he should have.
Attach is the patch that allows to turn off mhchem the same way as esint and amsmath. regards Uwe
