As egreg says, it can't be done in a generalized way. And in this answer, I don't have merriweather font, so I just demonstrate the technique (and exaggerate the effect) on the standard CM font.
One can locally achieve what you ask by making
- active; however, that breaks many, many things, because it means the negative sign has been redefined. So the compromise I propose here is a macro pair
\newhyphenOFF. In this way, you can turn
\newhyphenON when you are just typing text with your shifted hyphens, and turn it off for just about everything else.
In this MWE, I show how, when
\nehyphenOFF has been invoked, the minus sign is restored for use in a
\raisebox. But when
\nehyphenON is invoked, the shifted hyphen is in place.